Re: [GRASS-dev] Write array to (point) attribute table
On 01-10-15 17:49, Vaclav Petras wrote:
On Thu, Oct 1, 2015 at 11:28 AM, Paulo van Breugel
mailto:p.vanbreu...@gmail.com>> wrote:
with VectorTopo('testB', mode='rw') as vectormap:
At the and it makes sense. 'w' removes the vectors and starts over.
'rw' keep the file but ones it for writing. Perhaps 'a' would make
better sense in this case. What the documentation says?
On https://grass.osgeo.org/grass70/manuals/libpython/pygrass_vector.html
it is mentioned that:
"/The open() method supports a number of option arguments (see the Info
documentation for a complete list). In particular, the mode argument can
take a a value of r for reading, w for writing, or rw for
reading/writing." [...] /"/If a vector map is opened with the mode w or
rw, then the user can write new features to the dataset/".
I think this description is somewhat ambiguous. Especially the mode='w'
is unclear to me; I could clearly not write new features to an
(existing) vector layer. It might be nice to have a short one-line
explanation of each of these options, explaining the difference.
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Re: [GRASS-dev] Write array to (point) attribute table
On Thu, Oct 1, 2015 at 10:01 AM, Michel Wortmann
wrote:
> Hi Paulo,
> I had the same problem some time ago. I am using pandas for a lot of things
> and discovered the quickest way to append a column to a vector table is
> using pandas' .to_sql dataframe method. Here is my full function for it:
To add a ne column on an existing vector map in pygrass: write:
{{{
if 'column_name' in vect.table.columns:
vect.table.columns.drop('column_name')
vect.table.columns.add('column_name', 'column_type')
}}}
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Re: [GRASS-dev] Write array to (point) attribute table
On Thu, Oct 1, 2015 at 11:28 AM, Paulo van Breugel
wrote:
> with VectorTopo('testB', mode='rw') as vectormap:
At the and it makes sense. 'w' removes the vectors and starts over. 'rw'
keep the file but ones it for writing. Perhaps 'a' would make better sense
in this case. What the documentation says?
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Re: [GRASS-dev] Write array to (point) attribute table
Hi Michel,
Thanks! I think I got the suggestions by Anna, Pietro and Moritz
working, but this certainly looks like an handy function to have at
hand. One possible disadvantage if using this in a script to be shared
with others is that it would add an dependency on pandas, wouldn't it?
Cheers,
Paulo
On 01-10-15 10:01, Michel Wortmann wrote:
Hi Paulo,
I had the same problem some time ago. I am using pandas for a lot of
things and discovered the quickest way to append a column to a vector
table is using pandas' .to_sql dataframe method. Here is my full
function for it:
import pandas as pa
dataframe = pa.DataFrame( ... )
def appendColumns(vecttbl,dataframe,join=None,layer=1):
'''Upload a DataFrame (Series should be first converted into a sql
compliant datafram)
to a grass vector table. Join is a valid column in vecttbl or if None take
categories.
Always joins on df.index, which is not uploaded.'''
# get sqlite.db info
db = grass.vector_db(vecttbl)[layer]
con = sqlite3.connect(db['database'])
# decide join indeces
itbl = {False:db['key'],True:join}[join!=None]
# make series to dataframe
dataframe.to_sql('pandas_temp',con,if_exists='replace',index_label='ix') #
index label?
# join columns to vecttbl
grass.run_command('v.db.join',map=vecttbl,column=itbl,
other_table='pandas_temp',other_column='ix',
subset_columns=','.join(map(str,dataframe.columns)))
# remove temp table
cur = con.cursor()
cur.execute('DROP TABLE IF EXISTS pandas_temp')
con.commit(); con.close()
return
The dataframe.to_sql line is essentially all you need, the rest of the
function is just prepping.
Hope it helps,
Michel
On 10/01/2015 12:05 AM, Paulo van Breugel wrote:
On 30-09-15 17:52, Paulo van Breugel wrote:
On 30-09-15 17:47, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 11:20 AM, Paulo van Breugel
wrote:
On 30-09-15 16:18, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 9:27 AM, Paulo van Breugel
mailto:p.vanbreu...@gmail.com>> wrote:
On Wed, Sep 30, 2015 at 11:53 AM, Pietro
wrote:
On Wed, Sep 30, 2015 at 9:51 AM, Paulo van Breugel
wrote:
>
>
> On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová
> wrote:
>>
>>
>>
>> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
>> wrote:
>>>
>>> This must be a very basic question, but I can't
find an easy/direct way
>>> to do this. In python, if I have an array with
values with a length equal to
>>> the number of rows in an attribute table of a
(point) vector layer, how can
>>> I write those values to a new column in that
attribute table. I can of
>>> course first create the column, but than how to
update that column with the
>>> values in the array?
>>
>>
>> it should be pretty easy to do with pygrass,
unfortunately there is no
>> example on assigning attributes in the official
documentation [1], but it
>> should be pretty easy, something like that (not
tested):
>>
>> with VectorTopo('myvector', mode='w') as vectormap:
>> for feature in vectormap:
>> feature.attrs['mycolumn'] = value
>>
>>
> Thanks, but that seems to write the vector back
without attribute table
You have to save the changes in the database out from
your cycle, with:
vectormap.table.conn.commit()
Thanks Pietro. I am, however, not sure I understand (I
tried to use it, but thanks to my limited experience in
Python / pygrass not much luck). Just to be more specific,
I am trying to create a script that divides points in
training and test groups, similar to v.kcv, but with
points clustered in space. E.g.,
# Create vector
grass.run_command("v.random", output="testB", npoints=10,
overwrite=True)
grass.run_command("v.db.addtable", map="testB", columns="X
DOUBLE PRECISION,Y DOUBLE PRECISION,GR INTEGER")
grass.run_command("v.to.db", map="test", option="coor",
columns="X,Y")
# Create groups
vectmap = 'test'
cvals = array(grass.vector_db_select(vectmap, layer =
int(1), columns = 'X,Y')['values'].values()).astype(np.float)
centroids,_ = kmeans(cvals,2)
idx,_ = vq(cvals,centroids)
# write results to tabel
Now I would like to write idx to the column 'GR' in the
attribute table of 'test'.
p.s. I am first creating the XY columns now, but is there
Re: [GRASS-dev] Write array to (point) attribute table
On 01-10-15 09:15, Moritz Lennert wrote:
On 01/10/15 00:05, Paulo van Breugel wrote:
On 30-09-15 17:52, Paulo van Breugel wrote:
On 30-09-15 17:47, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 11:20 AM, Paulo van Breugel
wrote:
On 30-09-15 16:18, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 9:27 AM, Paulo van Breugel
mailto:p.vanbreu...@gmail.com>> wrote:
On Wed, Sep 30, 2015 at 11:53 AM, Pietro
wrote:
On Wed, Sep 30, 2015 at 9:51 AM, Paulo van Breugel
wrote:
>
>
> On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová
> wrote:
>>
>>
>>
>> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
>> wrote:
>>>
>>> This must be a very basic question, but I can't find
an easy/direct way
>>> to do this. In python, if I have an array with
values with a length equal to
>>> the number of rows in an attribute table of a
(point) vector layer, how can
>>> I write those values to a new column in that
attribute table. I can of
>>> course first create the column, but than how to
update that column with the
>>> values in the array?
>>
>>
>> it should be pretty easy to do with pygrass,
unfortunately there is no
>> example on assigning attributes in the official
documentation [1], but it
>> should be pretty easy, something like that (not
tested):
>>
>> with VectorTopo('myvector', mode='w') as vectormap:
>> for feature in vectormap:
>> feature.attrs['mycolumn'] = value
>>
>>
> Thanks, but that seems to write the vector back
without attribute table
You have to save the changes in the database out from
your cycle, with:
vectormap.table.conn.commit()
Thanks Pietro. I am, however, not sure I understand (I tried
to use it, but thanks to my limited experience in Python /
pygrass not much luck). Just to be more specific, I am
trying to create a script that divides points in training
and test groups, similar to v.kcv, but with points clustered
in space. E.g.,
# Create vector
grass.run_command("v.random", output="testB", npoints=10,
overwrite=True)
grass.run_command("v.db.addtable", map="testB", columns="X
DOUBLE PRECISION,Y DOUBLE PRECISION,GR INTEGER")
grass.run_command("v.to.db", map="test", option="coor",
columns="X,Y")
# Create groups
vectmap = 'test'
cvals = array(grass.vector_db_select(vectmap, layer =
int(1), columns = 'X,Y')['values'].values()).astype(np.float)
centroids,_ = kmeans(cvals,2)
idx,_ = vq(cvals,centroids)
# write results to tabel
Now I would like to write idx to the column 'GR' in the
attribute table of 'test'.
p.s. I am first creating the XY columns now, but is there a
function to get the coordinates (cvals) in pygrass directly?
I don't fully understand the example,
Thanks for the quick response. I basically have a list with
values (idx in the example above) which I like to add as a column
to the attribute table of an existing vector (point layer). The
length of idx is equal to the number of rows in the attribute
table. The solution of Anna seems like an elegant solution (and
easier and more flexible than other solutions I tried using e.g.,
sqlite3). However, as I wrote, I end up with a vector without
attribute table. You wrote that I "have to save the changes in
the database out from your cycle, with:
vectormap.table.conn.commit()". I am, however, not sure what you
mean with 'out from your cycle' or how to implement that.
probably after the for cycle ends you would call this
'vectormap.table.conn.commit()', if it doesn't works, try to put it
in the cycle (I am not sure what is supposed to work).
I did try both, with no luck so-far. I'll give it another try though,
perhaps I did something else wrong.
Tried out again, but after running the code below, I end up with an
empty vector layer (no points and no attribute table). Same if I put the
vectormap.table.conn.commit() in the for cycle.
import grass.script as grass
from grass.pygrass.vector import VectorTopo
grass.run_command("v.random", output="testB", npoints=10,
overwrite=True)
grass.run_command("v.db.addtable", map="testB", columns="GR INTEGER")
with VectorTopo('testB', mode='w') as vectormap:
for feature in vectormap:
feature.attrs['GR'] = 9
vectormap.table.conn.commit()
Just a wild guess, here without looking at the libr
Re: [GRASS-dev] Write array to (point) attribute table
Hi Paulo,
I had the same problem some time ago. I am using pandas for a lot of
things and discovered the quickest way to append a column to a vector
table is using pandas' .to_sql dataframe method. Here is my full
function for it:
import pandas as pa
dataframe = pa.DataFrame( ... )
def appendColumns(vecttbl,dataframe,join=None,layer=1):
'''Upload a DataFrame (Series should be first converted into a sql
compliant datafram)
to a grass vector table. Join is a valid column in vecttbl or if None take
categories.
Always joins on df.index, which is not uploaded.'''
# get sqlite.db info
db = grass.vector_db(vecttbl)[layer]
con = sqlite3.connect(db['database'])
# decide join indeces
itbl = {False:db['key'],True:join}[join!=None]
# make series to dataframe
dataframe.to_sql('pandas_temp',con,if_exists='replace',index_label='ix') #
index label?
# join columns to vecttbl
grass.run_command('v.db.join',map=vecttbl,column=itbl,
other_table='pandas_temp',other_column='ix',
subset_columns=','.join(map(str,dataframe.columns)))
# remove temp table
cur = con.cursor()
cur.execute('DROP TABLE IF EXISTS pandas_temp')
con.commit(); con.close()
return
The dataframe.to_sql line is essentially all you need, the rest of the
function is just prepping.
Hope it helps,
Michel
On 10/01/2015 12:05 AM, Paulo van Breugel wrote:
On 30-09-15 17:52, Paulo van Breugel wrote:
On 30-09-15 17:47, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 11:20 AM, Paulo van Breugel
wrote:
On 30-09-15 16:18, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 9:27 AM, Paulo van Breugel
mailto:p.vanbreu...@gmail.com>> wrote:
On Wed, Sep 30, 2015 at 11:53 AM, Pietro
wrote:
On Wed, Sep 30, 2015 at 9:51 AM, Paulo van Breugel
wrote:
>
>
> On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová
> wrote:
>>
>>
>>
>> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
>> wrote:
>>>
>>> This must be a very basic question, but I can't
find an easy/direct way
>>> to do this. In python, if I have an array with
values with a length equal to
>>> the number of rows in an attribute table of a
(point) vector layer, how can
>>> I write those values to a new column in that
attribute table. I can of
>>> course first create the column, but than how to
update that column with the
>>> values in the array?
>>
>>
>> it should be pretty easy to do with pygrass,
unfortunately there is no
>> example on assigning attributes in the official
documentation [1], but it
>> should be pretty easy, something like that (not tested):
>>
>> with VectorTopo('myvector', mode='w') as vectormap:
>> for feature in vectormap:
>> feature.attrs['mycolumn'] = value
>>
>>
> Thanks, but that seems to write the vector back
without attribute table
You have to save the changes in the database out from
your cycle, with:
vectormap.table.conn.commit()
Thanks Pietro. I am, however, not sure I understand (I
tried to use it, but thanks to my limited experience in
Python / pygrass not much luck). Just to be more specific,
I am trying to create a script that divides points in
training and test groups, similar to v.kcv, but with points
clustered in space. E.g.,
# Create vector
grass.run_command("v.random", output="testB", npoints=10,
overwrite=True)
grass.run_command("v.db.addtable", map="testB", columns="X
DOUBLE PRECISION,Y DOUBLE PRECISION,GR INTEGER")
grass.run_command("v.to.db", map="test", option="coor",
columns="X,Y")
# Create groups
vectmap = 'test'
cvals = array(grass.vector_db_select(vectmap, layer =
int(1), columns = 'X,Y')['values'].values()).astype(np.float)
centroids,_ = kmeans(cvals,2)
idx,_ = vq(cvals,centroids)
# write results to tabel
Now I would like to write idx to the column 'GR' in the
attribute table of 'test'.
p.s. I am first creating the XY columns now, but is there a
function to get the coordinates (cvals) in pygrass directly?
I don't fully understand the example,
Thanks for the quick response. I basically have a list with
values (idx in the example above) which I like to add as a
column to the attribute table of an existing vector (point
layer). The length of idx is equal to the number of rows
Re: [GRASS-dev] Write array to (point) attribute table
On 01/10/15 00:05, Paulo van Breugel wrote:
On 30-09-15 17:52, Paulo van Breugel wrote:
On 30-09-15 17:47, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 11:20 AM, Paulo van Breugel
wrote:
On 30-09-15 16:18, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 9:27 AM, Paulo van Breugel
mailto:p.vanbreu...@gmail.com>> wrote:
On Wed, Sep 30, 2015 at 11:53 AM, Pietro
wrote:
On Wed, Sep 30, 2015 at 9:51 AM, Paulo van Breugel
wrote:
>
>
> On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová
> wrote:
>>
>>
>>
>> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
>> wrote:
>>>
>>> This must be a very basic question, but I can't find
an easy/direct way
>>> to do this. In python, if I have an array with
values with a length equal to
>>> the number of rows in an attribute table of a
(point) vector layer, how can
>>> I write those values to a new column in that
attribute table. I can of
>>> course first create the column, but than how to
update that column with the
>>> values in the array?
>>
>>
>> it should be pretty easy to do with pygrass,
unfortunately there is no
>> example on assigning attributes in the official
documentation [1], but it
>> should be pretty easy, something like that (not tested):
>>
>> with VectorTopo('myvector', mode='w') as vectormap:
>> for feature in vectormap:
>> feature.attrs['mycolumn'] = value
>>
>>
> Thanks, but that seems to write the vector back
without attribute table
You have to save the changes in the database out from
your cycle, with:
vectormap.table.conn.commit()
Thanks Pietro. I am, however, not sure I understand (I tried
to use it, but thanks to my limited experience in Python /
pygrass not much luck). Just to be more specific, I am
trying to create a script that divides points in training
and test groups, similar to v.kcv, but with points clustered
in space. E.g.,
# Create vector
grass.run_command("v.random", output="testB", npoints=10,
overwrite=True)
grass.run_command("v.db.addtable", map="testB", columns="X
DOUBLE PRECISION,Y DOUBLE PRECISION,GR INTEGER")
grass.run_command("v.to.db", map="test", option="coor",
columns="X,Y")
# Create groups
vectmap = 'test'
cvals = array(grass.vector_db_select(vectmap, layer =
int(1), columns = 'X,Y')['values'].values()).astype(np.float)
centroids,_ = kmeans(cvals,2)
idx,_ = vq(cvals,centroids)
# write results to tabel
Now I would like to write idx to the column 'GR' in the
attribute table of 'test'.
p.s. I am first creating the XY columns now, but is there a
function to get the coordinates (cvals) in pygrass directly?
I don't fully understand the example,
Thanks for the quick response. I basically have a list with
values (idx in the example above) which I like to add as a column
to the attribute table of an existing vector (point layer). The
length of idx is equal to the number of rows in the attribute
table. The solution of Anna seems like an elegant solution (and
easier and more flexible than other solutions I tried using e.g.,
sqlite3). However, as I wrote, I end up with a vector without
attribute table. You wrote that I "have to save the changes in
the database out from your cycle, with:
vectormap.table.conn.commit()". I am, however, not sure what you
mean with 'out from your cycle' or how to implement that.
probably after the for cycle ends you would call this
'vectormap.table.conn.commit()', if it doesn't works, try to put it
in the cycle (I am not sure what is supposed to work).
I did try both, with no luck so-far. I'll give it another try though,
perhaps I did something else wrong.
Tried out again, but after running the code below, I end up with an
empty vector layer (no points and no attribute table). Same if I put the
vectormap.table.conn.commit() in the for cycle.
import grass.script as grass
from grass.pygrass.vector import VectorTopo
grass.run_command("v.random", output="testB", npoints=10, overwrite=True)
grass.run_command("v.db.addtable", map="testB", columns="GR INTEGER")
with VectorTopo('testB', mode='w') as vectormap:
for feature in vectormap:
feature.attrs['GR'] = 9
vectormap.table.conn.commit()
Just a wild guess, here without looking at the library code, but could
it be that it should be
V
Re: [GRASS-dev] Write array to (point) attribute table
On 30-09-15 17:52, Paulo van Breugel wrote:
On 30-09-15 17:47, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 11:20 AM, Paulo van Breugel
wrote:
On 30-09-15 16:18, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 9:27 AM, Paulo van Breugel
mailto:p.vanbreu...@gmail.com>> wrote:
On Wed, Sep 30, 2015 at 11:53 AM, Pietro
wrote:
On Wed, Sep 30, 2015 at 9:51 AM, Paulo van Breugel
wrote:
>
>
> On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová
> wrote:
>>
>>
>>
>> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
>> wrote:
>>>
>>> This must be a very basic question, but I can't find
an easy/direct way
>>> to do this. In python, if I have an array with
values with a length equal to
>>> the number of rows in an attribute table of a
(point) vector layer, how can
>>> I write those values to a new column in that
attribute table. I can of
>>> course first create the column, but than how to
update that column with the
>>> values in the array?
>>
>>
>> it should be pretty easy to do with pygrass,
unfortunately there is no
>> example on assigning attributes in the official
documentation [1], but it
>> should be pretty easy, something like that (not tested):
>>
>> with VectorTopo('myvector', mode='w') as vectormap:
>> for feature in vectormap:
>> feature.attrs['mycolumn'] = value
>>
>>
> Thanks, but that seems to write the vector back
without attribute table
You have to save the changes in the database out from
your cycle, with:
vectormap.table.conn.commit()
Thanks Pietro. I am, however, not sure I understand (I tried
to use it, but thanks to my limited experience in Python /
pygrass not much luck). Just to be more specific, I am
trying to create a script that divides points in training
and test groups, similar to v.kcv, but with points clustered
in space. E.g.,
# Create vector
grass.run_command("v.random", output="testB", npoints=10,
overwrite=True)
grass.run_command("v.db.addtable", map="testB", columns="X
DOUBLE PRECISION,Y DOUBLE PRECISION,GR INTEGER")
grass.run_command("v.to.db", map="test", option="coor",
columns="X,Y")
# Create groups
vectmap = 'test'
cvals = array(grass.vector_db_select(vectmap, layer =
int(1), columns = 'X,Y')['values'].values()).astype(np.float)
centroids,_ = kmeans(cvals,2)
idx,_ = vq(cvals,centroids)
# write results to tabel
Now I would like to write idx to the column 'GR' in the
attribute table of 'test'.
p.s. I am first creating the XY columns now, but is there a
function to get the coordinates (cvals) in pygrass directly?
I don't fully understand the example,
Thanks for the quick response. I basically have a list with
values (idx in the example above) which I like to add as a column
to the attribute table of an existing vector (point layer). The
length of idx is equal to the number of rows in the attribute
table. The solution of Anna seems like an elegant solution (and
easier and more flexible than other solutions I tried using e.g.,
sqlite3). However, as I wrote, I end up with a vector without
attribute table. You wrote that I "have to save the changes in
the database out from your cycle, with:
vectormap.table.conn.commit()". I am, however, not sure what you
mean with 'out from your cycle' or how to implement that.
probably after the for cycle ends you would call this
'vectormap.table.conn.commit()', if it doesn't works, try to put it
in the cycle (I am not sure what is supposed to work).
I did try both, with no luck so-far. I'll give it another try though,
perhaps I did something else wrong.
Tried out again, but after running the code below, I end up with an
empty vector layer (no points and no attribute table). Same if I put the
vectormap.table.conn.commit() in the for cycle.
import grass.script as grass
from grass.pygrass.vector import VectorTopo
grass.run_command("v.random", output="testB", npoints=10, overwrite=True)
grass.run_command("v.db.addtable", map="testB", columns="GR INTEGER")
with VectorTopo('testB', mode='w') as vectormap:
for feature in vectormap:
feature.attrs['GR'] = 9
vectormap.table.conn.commit()
but yes, you can get coordinates:
with VectorTopo('myvector', mode='w') as vectormap:
for feature in vectormap:
prin
Re: [GRASS-dev] Write array to (point) attribute table
On 30-09-15 17:47, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 11:20 AM, Paulo van Breugel
mailto:p.vanbreu...@gmail.com>> wrote:
On 30-09-15 16:18, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 9:27 AM, Paulo van Breugel
mailto:p.vanbreu...@gmail.com>> wrote:
On Wed, Sep 30, 2015 at 11:53 AM, Pietro
mailto:peter.z...@gmail.com>> wrote:
On Wed, Sep 30, 2015 at 9:51 AM, Paulo van Breugel
mailto:p.vanbreu...@gmail.com>>
wrote:
>
>
> On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová
mailto:kratocha...@gmail.com>>
> wrote:
>>
>>
>>
>> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
>> mailto:p.vanbreu...@gmail.com>> wrote:
>>>
>>> This must be a very basic question, but I can't find
an easy/direct way
>>> to do this. In python, if I have an array with values
with a length equal to
>>> the number of rows in an attribute table of a (point)
vector layer, how can
>>> I write those values to a new column in that
attribute table. I can of
>>> course first create the column, but than how to
update that column with the
>>> values in the array?
>>
>>
>> it should be pretty easy to do with pygrass,
unfortunately there is no
>> example on assigning attributes in the official
documentation [1], but it
>> should be pretty easy, something like that (not tested):
>>
>> with VectorTopo('myvector', mode='w') as vectormap:
>> for feature in vectormap:
>> feature.attrs['mycolumn'] = value
>>
>>
> Thanks, but that seems to write the vector back without
attribute table
You have to save the changes in the database out from
your cycle, with:
vectormap.table.conn.commit()
Thanks Pietro. I am, however, not sure I understand (I tried
to use it, but thanks to my limited experience in Python /
pygrass not much luck). Just to be more specific, I am trying
to create a script that divides points in training and test
groups, similar to v.kcv, but with points clustered in space.
E.g.,
# Create vector
grass.run_command("v.random", output="testB", npoints=10,
overwrite=True)
grass.run_command("v.db.addtable", map="testB", columns="X
DOUBLE PRECISION,Y DOUBLE PRECISION,GR INTEGER")
grass.run_command("v.to.db", map="test", option="coor",
columns="X,Y")
# Create groups
vectmap = 'test'
cvals = array(grass.vector_db_select(vectmap, layer = int(1),
columns = 'X,Y')['values'].values()).astype(np.float)
centroids,_ = kmeans(cvals,2)
idx,_ = vq(cvals,centroids)
# write results to tabel
Now I would like to write idx to the column 'GR' in the
attribute table of 'test'.
p.s. I am first creating the XY columns now, but is there a
function to get the coordinates (cvals) in pygrass directly?
I don't fully understand the example,
Thanks for the quick response. I basically have a list with values
(idx in the example above) which I like to add as a column to the
attribute table of an existing vector (point layer). The length of
idx is equal to the number of rows in the attribute table. The
solution of Anna seems like an elegant solution (and easier and
more flexible than other solutions I tried using e.g., sqlite3).
However, as I wrote, I end up with a vector without attribute
table. You wrote that I "have to save the changes in the database
out from your cycle, with: vectormap.table.conn.commit()". I am,
however, not sure what you mean with 'out from your cycle' or how
to implement that.
probably after the for cycle ends you would call this
'vectormap.table.conn.commit()', if it doesn't works, try to put it in
the cycle (I am not sure what is supposed to work).
I did try both, with no luck so-far. I'll give it another try though,
perhaps I did something else wrong.
but yes, you can get coordinates:
with VectorTopo('myvector', mode='w') as vectormap:
for feature in vectormap:
print feature.x
print feature.y
Great, thanks. I did not find this in the manual. If it is not
there, perhaps it would be something worth including? I would not
mind providing a text, but I am not sure what would be the best
way to do that.
Technically, it's in the manual:
https://grass.osgeo.org/grass70/manuals/libpython/pygrass_vector.html#geometry-classes
but we are lacking more examples of often used constructions. S
Re: [GRASS-dev] Write array to (point) attribute table
On Wed, Sep 30, 2015 at 11:20 AM, Paulo van Breugel
wrote:
>
>
> On 30-09-15 16:18, Anna Petrášová wrote:
>
>
>
> On Wed, Sep 30, 2015 at 9:27 AM, Paulo van Breugel <
> p.vanbreu...@gmail.com> wrote:
>
>>
>>
>> On Wed, Sep 30, 2015 at 11:53 AM, Pietro <
>> peter.z...@gmail.com> wrote:
>>
>>> On Wed, Sep 30, 2015 at 9:51 AM, Paulo van Breugel
>>> wrote:
>>> >
>>> >
>>> > On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová >> >
>>> > wrote:
>>> >>
>>> >>
>>> >>
>>> >> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
>>> >> wrote:
>>> >>>
>>> >>> This must be a very basic question, but I can't find an easy/direct
>>> way
>>> >>> to do this. In python, if I have an array with values with a length
>>> equal to
>>> >>> the number of rows in an attribute table of a (point) vector layer,
>>> how can
>>> >>> I write those values to a new column in that attribute table. I can
>>> of
>>> >>> course first create the column, but than how to update that column
>>> with the
>>> >>> values in the array?
>>> >>
>>> >>
>>> >> it should be pretty easy to do with pygrass, unfortunately there is no
>>> >> example on assigning attributes in the official documentation [1],
>>> but it
>>> >> should be pretty easy, something like that (not tested):
>>> >>
>>> >> with VectorTopo('myvector', mode='w') as vectormap:
>>> >> for feature in vectormap:
>>> >> feature.attrs['mycolumn'] = value
>>> >>
>>> >>
>>> > Thanks, but that seems to write the vector back without attribute table
>>>
>>> You have to save the changes in the database out from your cycle, with:
>>>
>>> vectormap.table.conn.commit()
>>>
>>
>> Thanks Pietro. I am, however, not sure I understand (I tried to use it,
>> but thanks to my limited experience in Python / pygrass not much luck).
>> Just to be more specific, I am trying to create a script that divides
>> points in training and test groups, similar to v.kcv, but with points
>> clustered in space. E.g.,
>>
>> # Create vector
>> grass.run_command("v.random", output="testB", npoints=10, overwrite=True)
>> grass.run_command("v.db.addtable", map="testB", columns="X DOUBLE
>> PRECISION,Y DOUBLE PRECISION,GR INTEGER")
>> grass.run_command("v.to.db", map="test", option="coor", columns="X,Y")
>>
>> # Create groups
>> vectmap = 'test'
>> cvals = array(grass.vector_db_select(vectmap, layer = int(1), columns =
>> 'X,Y')['values'].values()).astype(np.float)
>> centroids,_ = kmeans(cvals,2)
>> idx,_ = vq(cvals,centroids)
>>
>> # write results to tabel
>> Now I would like to write idx to the column 'GR' in the attribute table
>> of 'test'.
>>
>> p.s. I am first creating the XY columns now, but is there a function to
>> get the coordinates (cvals) in pygrass directly?
>>
>>
>> I don't fully understand the example,
>
>
> Thanks for the quick response. I basically have a list with values (idx in
> the example above) which I like to add as a column to the attribute table
> of an existing vector (point layer). The length of idx is equal to the
> number of rows in the attribute table. The solution of Anna seems like an
> elegant solution (and easier and more flexible than other solutions I tried
> using e.g., sqlite3). However, as I wrote, I end up with a vector without
> attribute table. You wrote that I "have to save the changes in the database
> out from your cycle, with: vectormap.table.conn.commit()". I am, however,
> not sure what you mean with 'out from your cycle' or how to implement that.
>
probably after the for cycle ends you would call this
'vectormap.table.conn.commit()', if it doesn't works, try to put it in the
cycle (I am not sure what is supposed to work).
>
> but yes, you can get coordinates:
>
> with VectorTopo('myvector', mode='w') as vectormap:
> for feature in vectormap:
> print feature.x
> print feature.y
>
>
> Great, thanks. I did not find this in the manual. If it is not there,
> perhaps it would be something worth including? I would not mind providing a
> text, but I am not sure what would be the best way to do that.
>
Technically, it's in the manual:
https://grass.osgeo.org/grass70/manuals/libpython/pygrass_vector.html#geometry-classes
but we are lacking more examples of often used constructions. Some other
examples are available in the recent workshop we did:
https://github.com/wenzeslaus/python-grass-addon/blob/master/02_pygrass_library.ipynb
>
>
>>
>>
>>>
>>> Pietro
>>>
>>
>>
>
>
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Re: [GRASS-dev] Write array to (point) attribute table
On 30-09-15 16:18, Anna Petrášová wrote:
On Wed, Sep 30, 2015 at 9:27 AM, Paulo van Breugel
mailto:p.vanbreu...@gmail.com>> wrote:
On Wed, Sep 30, 2015 at 11:53 AM, Pietro mailto:peter.z...@gmail.com>> wrote:
On Wed, Sep 30, 2015 at 9:51 AM, Paulo van Breugel
mailto:p.vanbreu...@gmail.com>> wrote:
>
>
> On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová
mailto:kratocha...@gmail.com>>
> wrote:
>>
>>
>>
>> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
>> mailto:p.vanbreu...@gmail.com>> wrote:
>>>
>>> This must be a very basic question, but I can't find an
easy/direct way
>>> to do this. In python, if I have an array with values with
a length equal to
>>> the number of rows in an attribute table of a (point)
vector layer, how can
>>> I write those values to a new column in that attribute
table. I can of
>>> course first create the column, but than how to update
that column with the
>>> values in the array?
>>
>>
>> it should be pretty easy to do with pygrass, unfortunately
there is no
>> example on assigning attributes in the official
documentation [1], but it
>> should be pretty easy, something like that (not tested):
>>
>> with VectorTopo('myvector', mode='w') as vectormap:
>> for feature in vectormap:
>> feature.attrs['mycolumn'] = value
>>
>>
> Thanks, but that seems to write the vector back without
attribute table
You have to save the changes in the database out from your
cycle, with:
vectormap.table.conn.commit()
Thanks Pietro. I am, however, not sure I understand (I tried to
use it, but thanks to my limited experience in Python / pygrass
not much luck). Just to be more specific, I am trying to create a
script that divides points in training and test groups, similar to
v.kcv, but with points clustered in space. E.g.,
# Create vector
grass.run_command("v.random", output="testB", npoints=10,
overwrite=True)
grass.run_command("v.db.addtable", map="testB", columns="X DOUBLE
PRECISION,Y DOUBLE PRECISION,GR INTEGER")
grass.run_command("v.to.db", map="test", option="coor", columns="X,Y")
# Create groups
vectmap = 'test'
cvals = array(grass.vector_db_select(vectmap, layer = int(1),
columns = 'X,Y')['values'].values()).astype(np.float)
centroids,_ = kmeans(cvals,2)
idx,_ = vq(cvals,centroids)
# write results to tabel
Now I would like to write idx to the column 'GR' in the attribute
table of 'test'.
p.s. I am first creating the XY columns now, but is there a
function to get the coordinates (cvals) in pygrass directly?
I don't fully understand the example,
Thanks for the quick response. I basically have a list with values (idx
in the example above) which I like to add as a column to the attribute
table of an existing vector (point layer). The length of idx is equal to
the number of rows in the attribute table. The solution of Anna seems
like an elegant solution (and easier and more flexible than other
solutions I tried using e.g., sqlite3). However, as I wrote, I end up
with a vector without attribute table. You wrote that I "have to save
the changes in the database out from your cycle, with:
vectormap.table.conn.commit()". I am, however, not sure what you mean
with 'out from your cycle' or how to implement that.
but yes, you can get coordinates:
with VectorTopo('myvector', mode='w') as vectormap:
for feature in vectormap:
print feature.x
print feature.y
Great, thanks. I did not find this in the manual. If it is not there,
perhaps it would be something worth including? I would not mind
providing a text, but I am not sure what would be the best way to do that.
Pietro
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Re: [GRASS-dev] Write array to (point) attribute table
On Wed, Sep 30, 2015 at 9:27 AM, Paulo van Breugel
wrote:
>
>
> On Wed, Sep 30, 2015 at 11:53 AM, Pietro wrote:
>
>> On Wed, Sep 30, 2015 at 9:51 AM, Paulo van Breugel
>> wrote:
>> >
>> >
>> > On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová
>> > wrote:
>> >>
>> >>
>> >>
>> >> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
>> >> wrote:
>> >>>
>> >>> This must be a very basic question, but I can't find an easy/direct
>> way
>> >>> to do this. In python, if I have an array with values with a length
>> equal to
>> >>> the number of rows in an attribute table of a (point) vector layer,
>> how can
>> >>> I write those values to a new column in that attribute table. I can of
>> >>> course first create the column, but than how to update that column
>> with the
>> >>> values in the array?
>> >>
>> >>
>> >> it should be pretty easy to do with pygrass, unfortunately there is no
>> >> example on assigning attributes in the official documentation [1],
>> but it
>> >> should be pretty easy, something like that (not tested):
>> >>
>> >> with VectorTopo('myvector', mode='w') as vectormap:
>> >> for feature in vectormap:
>> >> feature.attrs['mycolumn'] = value
>> >>
>> >>
>> > Thanks, but that seems to write the vector back without attribute table
>>
>> You have to save the changes in the database out from your cycle, with:
>>
>> vectormap.table.conn.commit()
>>
>
> Thanks Pietro. I am, however, not sure I understand (I tried to use it,
> but thanks to my limited experience in Python / pygrass not much luck).
> Just to be more specific, I am trying to create a script that divides
> points in training and test groups, similar to v.kcv, but with points
> clustered in space. E.g.,
>
> # Create vector
> grass.run_command("v.random", output="testB", npoints=10, overwrite=True)
> grass.run_command("v.db.addtable", map="testB", columns="X DOUBLE
> PRECISION,Y DOUBLE PRECISION,GR INTEGER")
> grass.run_command("v.to.db", map="test", option="coor", columns="X,Y")
>
> # Create groups
> vectmap = 'test'
> cvals = array(grass.vector_db_select(vectmap, layer = int(1), columns =
> 'X,Y')['values'].values()).astype(np.float)
> centroids,_ = kmeans(cvals,2)
> idx,_ = vq(cvals,centroids)
>
> # write results to tabel
> Now I would like to write idx to the column 'GR' in the attribute table of
> 'test'.
>
> p.s. I am first creating the XY columns now, but is there a function to
> get the coordinates (cvals) in pygrass directly?
>
>
> I don't fully understand the example, but yes, you can get coordinates:
with VectorTopo('myvector', mode='w') as vectormap:
for feature in vectormap:
print feature.x
print feature.y
>
>
>>
>> Pietro
>>
>
>
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Re: [GRASS-dev] Write array to (point) attribute table
On 30/09/15 15:27, Paulo van Breugel wrote:
On Wed, Sep 30, 2015 at 11:53 AM, Pietro mailto:peter.z...@gmail.com>> wrote:
On Wed, Sep 30, 2015 at 9:51 AM, Paulo van Breugel
mailto:p.vanbreu...@gmail.com>> wrote:
>
>
> On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová mailto:kratocha...@gmail.com>>
> wrote:
>>
>>
>>
>> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
>> mailto:p.vanbreu...@gmail.com>> wrote:
>>>
>>> This must be a very basic question, but I can't find an easy/direct way
>>> to do this. In python, if I have an array with values with a length
equal to
>>> the number of rows in an attribute table of a (point) vector layer, how
can
>>> I write those values to a new column in that attribute table. I can of
>>> course first create the column, but than how to update that column with
the
>>> values in the array?
>>
>>
>> it should be pretty easy to do with pygrass, unfortunately there is no
>> example on assigning attributes in the official documentation [1], but
it
>> should be pretty easy, something like that (not tested):
>>
>> with VectorTopo('myvector', mode='w') as vectormap:
>> for feature in vectormap:
>> feature.attrs['mycolumn'] = value
>>
>>
> Thanks, but that seems to write the vector back without attribute table
You have to save the changes in the database out from your cycle, with:
vectormap.table.conn.commit()
Thanks Pietro. I am, however, not sure I understand (I tried to use it,
but thanks to my limited experience in Python / pygrass not much luck).
Just to be more specific, I am trying to create a script that divides
points in training and test groups, similar to v.kcv, but with points
clustered in space. E.g.,
# Create vector
grass.run_command("v.random", output="testB", npoints=10, overwrite=True)
grass.run_command("v.db.addtable", map="testB", columns="X DOUBLE
PRECISION,Y DOUBLE PRECISION,GR INTEGER")
grass.run_command("v.to.db", map="test", option="coor", columns="X,Y")
# Create groups
vectmap = 'test'
cvals = array(grass.vector_db_select(vectmap, layer = int(1), columns =
'X,Y')['values'].values()).astype(np.float)
centroids,_ = kmeans(cvals,2)
idx,_ = vq(cvals,centroids)
# write results to tabel
Now I would like to write idx to the column 'GR' in the attribute table
of 'test'.
p.s. I am first creating the XY columns now, but is there a function to
get the coordinates (cvals) in pygrass directly?
Pygrass has other options, but you can always call v.to.db with the -p
flag and read the output directly. See one example at [1].
Moritz
[1]
https://trac.osgeo.org/grass/browser/grass-addons/grass7/vector/v.centerline/v.centerline.py#L198
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Re: [GRASS-dev] Write array to (point) attribute table
On Wed, Sep 30, 2015 at 11:53 AM, Pietro wrote:
> On Wed, Sep 30, 2015 at 9:51 AM, Paulo van Breugel
> wrote:
> >
> >
> > On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová
> > wrote:
> >>
> >>
> >>
> >> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
> >> wrote:
> >>>
> >>> This must be a very basic question, but I can't find an easy/direct way
> >>> to do this. In python, if I have an array with values with a length
> equal to
> >>> the number of rows in an attribute table of a (point) vector layer,
> how can
> >>> I write those values to a new column in that attribute table. I can of
> >>> course first create the column, but than how to update that column
> with the
> >>> values in the array?
> >>
> >>
> >> it should be pretty easy to do with pygrass, unfortunately there is no
> >> example on assigning attributes in the official documentation [1], but
> it
> >> should be pretty easy, something like that (not tested):
> >>
> >> with VectorTopo('myvector', mode='w') as vectormap:
> >> for feature in vectormap:
> >> feature.attrs['mycolumn'] = value
> >>
> >>
> > Thanks, but that seems to write the vector back without attribute table
>
> You have to save the changes in the database out from your cycle, with:
>
> vectormap.table.conn.commit()
>
Thanks Pietro. I am, however, not sure I understand (I tried to use it, but
thanks to my limited experience in Python / pygrass not much luck). Just to
be more specific, I am trying to create a script that divides points in
training and test groups, similar to v.kcv, but with points clustered in
space. E.g.,
# Create vector
grass.run_command("v.random", output="testB", npoints=10, overwrite=True)
grass.run_command("v.db.addtable", map="testB", columns="X DOUBLE
PRECISION,Y DOUBLE PRECISION,GR INTEGER")
grass.run_command("v.to.db", map="test", option="coor", columns="X,Y")
# Create groups
vectmap = 'test'
cvals = array(grass.vector_db_select(vectmap, layer = int(1), columns =
'X,Y')['values'].values()).astype(np.float)
centroids,_ = kmeans(cvals,2)
idx,_ = vq(cvals,centroids)
# write results to tabel
Now I would like to write idx to the column 'GR' in the attribute table of
'test'.
p.s. I am first creating the XY columns now, but is there a function to get
the coordinates (cvals) in pygrass directly?
>
> Pietro
>
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Re: [GRASS-dev] Write array to (point) attribute table
On Wed, Sep 30, 2015 at 9:51 AM, Paulo van Breugel
wrote:
>
>
> On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová
> wrote:
>>
>>
>>
>> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
>> wrote:
>>>
>>> This must be a very basic question, but I can't find an easy/direct way
>>> to do this. In python, if I have an array with values with a length equal to
>>> the number of rows in an attribute table of a (point) vector layer, how can
>>> I write those values to a new column in that attribute table. I can of
>>> course first create the column, but than how to update that column with the
>>> values in the array?
>>
>>
>> it should be pretty easy to do with pygrass, unfortunately there is no
>> example on assigning attributes in the official documentation [1], but it
>> should be pretty easy, something like that (not tested):
>>
>> with VectorTopo('myvector', mode='w') as vectormap:
>> for feature in vectormap:
>> feature.attrs['mycolumn'] = value
>>
>>
> Thanks, but that seems to write the vector back without attribute table
You have to save the changes in the database out from your cycle, with:
vectormap.table.conn.commit()
Pietro
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Re: [GRASS-dev] Write array to (point) attribute table
On Wed, Sep 30, 2015 at 2:02 AM, Anna Petrášová
wrote:
>
>
> On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel > wrote:
>
>> This must be a very basic question, but I can't find an easy/direct way
>> to do this. In python, if I have an array with values with a length equal
>> to the number of rows in an attribute table of a (point) vector layer, how
>> can I write those values to a new column in that attribute table. I can of
>> course first create the column, but than how to update that column with the
>> values in the array?
>>
>
> it should be pretty easy to do with pygrass, unfortunately there is no
> example on assigning attributes in the official documentation [1], but it
> should be pretty easy, something like that (not tested):
>
> with VectorTopo('myvector', mode='w') as vectormap:
> for feature in vectormap:
> feature.attrs['mycolumn'] = value
>
>
> Thanks, but that seems to write the vector back without attribute table
> Anna
>
> [1]
> https://grass.osgeo.org/grass70/manuals/libpython/pygrass_vector.html#working-with-vector-objects
>
>>
>> Cheers,
>>
>> Paulo
>>
>> ___
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>>
>
>
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Re: [GRASS-dev] Write array to (point) attribute table
On Tue, Sep 29, 2015 at 6:09 PM, Paulo van Breugel
wrote:
> This must be a very basic question, but I can't find an easy/direct way to
> do this. In python, if I have an array with values with a length equal to
> the number of rows in an attribute table of a (point) vector layer, how can
> I write those values to a new column in that attribute table. I can of
> course first create the column, but than how to update that column with the
> values in the array?
>
it should be pretty easy to do with pygrass, unfortunately there is no
example on assigning attributes in the official documentation [1], but it
should be pretty easy, something like that (not tested):
with VectorTopo('myvector', mode='w') as vectormap:
for feature in vectormap:
feature.attrs['mycolumn'] = value
Anna
[1]
https://grass.osgeo.org/grass70/manuals/libpython/pygrass_vector.html#working-with-vector-objects
>
> Cheers,
>
> Paulo
>
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>
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[GRASS-dev] Write array to (point) attribute table
This must be a very basic question, but I can't find an easy/direct way to do this. In python, if I have an array with values with a length equal to the number of rows in an attribute table of a (point) vector layer, how can I write those values to a new column in that attribute table. I can of course first create the column, but than how to update that column with the values in the array? Cheers, Paulo ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
