I've set up the data file with comma delimiter and one space. Split command
now:
(lat,lon)=line.strip().split(',')
Code runs without error but no points on the map. These two lines, however, do
produce an asterisk at the proper location:
xpt,ypt = m(-75.0,43.0)
text(xpt,ypt,'*')
I will strip the code down to bare minimum (take out reading of netCDF data
file) and paste it here along with ten example lats,lons.
--- On Tue, 4/19/11, Ian Bell <ib...@purdue.edu> wrote:
From: Ian Bell <ib...@purdue.edu>
Subject: Re: [Matplotlib-users] plotting points/locations from data file
To: "Michael Rawlins" <rawlin...@yahoo.com>
Cc: Matplotlib-users@lists.sourceforge.net
Date: Tuesday, April 19, 2011, 7:32 PM
The easiest solution would be to put a comma as the delimiter between the lat
and lon, and then change split(' ') to split(','). Then everything should work
fine. I exclusively work with comma separated files for this exact reason.
You are right that I had a typo, it should be lons[i]. It looks like you have
two spaces as the delimiter currently based on your copy-paste. That's why
split doesn't give you two values. In general I recommend that you avoid two
spaces as the delimiter, just going to cause problems.
----
Ian Bell
Graduate Research Assistant
Herrick Labs
Purdue University
email: ib...@purdue.edu
cell: (607)227-7626
On Tue, Apr 19, 2011 at 7:26 PM, Michael Rawlins <rawlin...@yahoo.com> wrote:
Sorry I should have mentioned that longitudes are negative; there is a '-'
before each longitude, like so:
39.4670 -76.1670
46.4000 -74.7670
45.3830 -75.7170
43.6170 -79.3830
45.5170 -73.4170
Also the plt.text line you sent had lon[i] rather than lons[i]. I corrected
that and changed my longitudes to not have the '-' sign and the code ran
without error. Could the '-' be causing a problem? I need to input the lat,
lon as in the file as shown above.
Mike
--- On Tue, 4/19/11, Ian Bell <ib...@purdue.edu> wrote:
From: Ian Bell <ib...@purdue.edu>
Subject: Re: [Matplotlib-users] plotting points/locations from data file
To: "Michael Rawlins"
<rawlin...@yahoo.com>
Cc: Matplotlib-users@lists.sourceforge.net
Date: Tuesday, April 19, 2011, 7:22 PM
If you want to plot a given marker at the point, for instance a circle, replace
the last line of my code plt.text...... with
plt.plot(lats,lons,'o')
for a circle, or
plt.plot(lats,lons,'s')
for a square. Refer to Plot for more information on the markers you can use.
You are getting the error because you have a delimiter different than a single
space, so it isn't splitting the line. Replace ' ' in the split command with
your whitespace delimiter. Is it a tab? Then you want '\t' .
Good luck,
Ian
----
Ian Bell
Graduate Research Assistant
Herrick Labs
Purdue University
email: ib...@purdue.edu
cell: (607)227-7626
On Tue, Apr 19, 2011 at 7:14 PM, Michael Rawlins <rawlin...@yahoo.com> wrote:
Yes, there is whitespace between each lat and lon on each line. But, actually,
I'd simply like to plot a dot at each location. The '1' was there in my
example because I do not yet know how to plot a particular symbol. Here is
what I got when I tried the code you just suggested.
Traceback (most recent call last):
File "test.py", line 319, in <module>
(lat,lon)=line.strip().split(' ')
ValueError: too many values to unpack
There are 203 records in the data file. Line 319 of test.py is this:
(lat,lon)=line.strip().split(' ')
--- On Tue, 4/19/11, Ian Bell <ib...@purdue.edu> wrote:
From: Ian Bell <ib...@purdue.edu>
Subject: Re:
[Matplotlib-users] plotting points/locations from data file
To: "Michael Rawlins" <rawlin...@yahoo.com>
Cc: Matplotlib-users@lists.sourceforge.net
Date: Tuesday, April 19, 2011, 6:52 PM
To clarify, you are trying to read in a set of (lat,lon) points in a file that
is space delimited, store the data, and then put a text marker at each point,
with each point numbered in order? The critical part is that you want to use a
list (or numpy array) instead of a dictionary. Something like this ought to do
(don't have MPL on this computer though - pretty sure this should work):
lines=open('file.txt','r').readlines()
(lats,lons)=([],[])
for line in lines:
(lat,lon)=line.strip().split(' ')
lats.append(float(lat))
lons.append(float(lon))
for i in range(len(lons)):
plt.text(lats[i],lon[i],str(i+1),ha='center',va='center',color='white')
I'm sure there are a bunch of more compact ways to do this, but this should
work.
Ian
----
Ian Bell
Graduate Research Assistant
Herrick Labs
Purdue University
email: ib...@purdue.edu
cell: (607)227-7626
On Tue, Apr 19, 2011 at 4:09 PM, Michael Rawlins <rawlin...@yahoo.com> wrote:
I'm trying to plot a series of points/locations on a map. I'm reading the
latitudes and longitudes from a file, with each lat, lon pair on each record
(line). Here is the code:
def make_float(line):
lati, longi = line.split()
return float(lati), float(longi)
my_dict = {}
with open("file.txt") as f:
for item in f:
lati,longi = make_float(item)
my_dict[lati] = longi
xpt,ypt = m(-76.1670,39.4670 )
plt.text(xpt,ypt,'1',color='white')
#print my_dict
The matplotlib code which I've previously used to plot a single point on the
map is below, with longitude and latitude in ( ):
xpt,ypt = m(-70.758392,42.960445)
plt.text(xpt,ypt,'1',color='white')
When replacing (-70.758392,42.960445) with (longi,lati), the code plots only a
single '1' at the location of just the last coordinate pair in the file. So now
I only need to plot them all. Does the code I've implemented have an implicit
loop to it?
Mike
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