On Mon, 13 Apr 2009, Zev Ross wrote:
Hi Alex,
Thank you so much for the suggestion and apologies for taking so long to test
it. I think the quotes are still a problem. I do indeed write all my code in
R-WinEdt but must be doing something wrong. In Python your suggested escaped
quotes works fine but perhaps I missed something in RPyGeo:
Is it possible that shQuote() might help here - maybe the multiple layers
are a problem, but quite often this function is good at guessing?
Roger
This code works in Python:
gp.makefeaturelayer("abc.shp", "walk")
gp.SelectLayerByAttribute('walk','NEW_SELECTION','\"hrwk05\" <> 0')
This code works in R:
rpygeo.geoprocessor(
"makefeaturelayer('abc.shp', 'walk')",
"SelectLayerByAttribute('walk','NEW_SELECTION','')",
env=myenv)
This code gives me an error in R:
rpygeo.geoprocessor(
"makefeaturelayer('abc.shp','walk')",
"SelectLayerByAttribute('walk','NEW_SELECTION','\"hrwk05\" <> 0')",
env=myenv)
File "x:\projects\rpygeo.py", line 10
gp.makefeaturelayer('abc.shp','walk')(
"SelectLayerByAttribute('walk','NEW_SELECTION','"hrwk05" <> 0')" )
^
SyntaxError: invalid syntax
NULL
(note from Zev -- the carrot occurs under the "05")
Alexander Brenning wrote:
Hi Zev,
the problems are definitely your quotes. First, they are syntactically
incorrect - I count seven double quotes (I recommend using some editor with
syntax highlighting, like Tinn-R or R-WinEdt, this helps discover
mismatches). Second, escaping them (\") should allow you to put double
quotes inside a double-quoted character string.
This might be closer to what you want to do (but I haven't tried to run it
- sorry, busy end of term...):
rpygeo.geoprocessor("makefeaturelayer('X:\\abc.shp','walk')",
"SelectLayerByAttribute('walk','NEW_SELECTION','\"hrwk05\"<>0')",
env=myenv)
Note that an additional argument clean.up=FALSE to the rpygeo.geoprocessor
allows you to inspect the Python file to check whether the quotes are
syntactically correct in Python.
I hope this helps
Alex
Zev Ross wrote:
Hi All,
I'm wondering if anybody could give me a little guidance on formatting a
query using RPyGeo. I'm excited to be able to run Python geoprocessing
functions straight from R but am having trouble with the quote, double
quote kinds of issues.
Here's an example of what I'd like to run
rpygeo.geoprocessor("makefeaturelayer('X:\\abc.shp',
'walk')", "SelectLayerByAttribute('walk','NEW_SELECTION', ' "hrwk05"
'<>0")",env=myenv)
Where the sticking point is hrwk05 <> 0. In Python my query would be
double quote, field name, close double quote, comparison, number e.g,
"hrwk05" <> 0 but I'm not sure how to put this into RPyGeo
If I run like so:
rpygeo.geoprocessor("makefeaturelayer('X:\\abc.shp',
'walk')", "SelectLayerByAttribute('walk','NEW_SELECTION', '')",env=myenv)
it runs.
Thank you in advance for assistance.
Zev
--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: roger.biv...@nhh.no
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