[R-sig-Geo] RPyGeo Query -- probably easy

Maarten van Strien maarten at vstrien.nl
Mon Dec 21 12:40:56 CET 2009


Thank you Alexander, your solution seems to work!

Best, Maarten


yes, the quotes are indeed tricky... The challenge is to provide the 
correct mix of escaped and un-escaped single and double quotes to Python 
/ ArcGIS as in this Python example:

gp.select_analysis("nfroads.shp", "paved.shp",
     ' "ROAD_CLASS" = \'PAVED\' ')

In order to achieve this, the backslashes in \' have to be escaped 
themselves, otherwise R will interpret them as escape symbols. After 
all, \' ends up being coded as \\\' in R. Also, double double-quotes 
have to be avoided; the quote.args argument of rpygeo.geoprocessor can 
be used to suppress the outermost double quotes, single quotes can be 
used explicitly instead: " ' sqlquery ' "

So here are two solutions:

env = rpygeo.build.env( workspace = "C:/TEMP",
               overwriteoutput = TRUE )

     list( "nfroads.shp", "paved.shp",
           " ' \"ROAD_CLASS\" = \\\'PAVED\\\' ' "),
     clean.up = FALSE, quote.args = c(T,T,F),
     env = env)

# alternative:

      env = env, clean.up = FALSE)

I hope this helps...

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