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When I try to run the R script "Summary statistics" in QGIS 2.12.1 on a Windows 7/64 bit machine, I get the error message "error in if (!file.info(DSN)$isdir) DSN missing value where TRUE/FALSE needed," and the output file is empty.

Having read a comment that R doesn't work properly if installed in the c:\Program Files\ directory, I tried installing it in its own directory in c:, but that didn't make any difference. I've tried installing R with and without the 32 bit files, and with just the 32 bit files (no 64 bit files), but the result is always the same: no results. The same happens with the R Histogram script.

QGIS's native Basic Statistics routine does produce results. Can anyone help me get R scripts working in QGIS?

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2 Answers 2

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i don't know the Windows version of R, but from what I know with other OS, you need to access R in the command line.

This mean that you can execute a R script in the console:

R(.exe ?) script.r

What happens when you invoke a R script (as Summary statistics), in Processing ?

1) the script /.../processing/algs/r/RUtils.py first create a R script file with the layer analysed in

/.../.qgis2/processing/processing_script.r

2) the content of this script is

options("repos"="http://cran.at.r-project.org/")
tryCatch(find.package("rgdal"), error=function(e) install.packages("rgdal", dependencies=TRUE))
tryCatch(find.package("raster"), error=function(e) install.packages("raster", dependencies=TRUE))
library("raster")
library("rgdal")
Layer = readOGR("/yourpath",layer="your_layer")
Field="test"
Summary_statistics<-data.frame(rbind(sum(Layer[[Field]]),
length(Layer[[Field]]),
length(unique(Layer[[Field]])),
min(Layer[[Field]]),
max(Layer[[Field]]),
max(Layer[[Field]])-min(Layer[[Field]]),
mean(Layer[[Field]]),
median(Layer[[Field]]),
sd(Layer[[Field]])),row.names=c("Sum:","Count:","Unique values:","Minimum value:","Maximum value:","Range:","Mean value:","Median value:","Standard deviation:"))
colnames(Summary_statistics)<-c(Field)
Summary_statistics

3) then the same Python script execute R processing_script.r with the module subprocess

I hope it will help you to understand your problem

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  • Thank you for responding. There is a library of R scripts that installs as part of QGIS and is accessible through the processing toolbox. That is what I am trying to get working. I have the latest version of R (3.2.3) installed.
    – Terry Morse
    Dec 28, 2015 at 4:38
  • I use also this library but the problem, as I say, is the availability of the R executable: R(.exe?) processing_script.r. Can you do that in the command line ?
    – gene
    Dec 28, 2015 at 9:24
  • When I tried to run the script, I got an invalid syntax error after the line, "tryCatch(find.package("rgdal"), error=function(e) install.packages("rgdal", dependencies=TRUE))." I don't know whether this is relevant, but I do have rgdal installed at C:\Users\Terry\.qgis2\processing\rlibs\rgdal and have set the path to rlibs correctly in Processing Options. Running the R summary statistics script again, I notice in the output that rgdal is successfully loaded, and the error occurs when it attempts to load the layer (Layer=readOGR(path to the layer). Does this help narrow down the problem any?
    – Terry Morse
    Dec 29, 2015 at 7:29
  • The correct format in the script is for example Layer = readOGR("/../.../test",layer="test") that is readOGR(path of the shapefile,layer=name of the shapefile (without.shp))
    – gene
    Dec 29, 2015 at 9:47
  • I have no experience with Python programming and am not sure what your are suggesting I do. I tried running the script you outlined above with my path, file name, and field name substituted in lines 6 and 7. I get an "invalid syntax" error on line 2. If you have the time and patience, I'll need this spelled out in more detail. Thank you.
    – Terry Morse
    Dec 30, 2015 at 5:58
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While QGIS will extract and process layers from a zipfile, it appears that the R scripts (and possibly others) can't. When I extracted the layers and added them to QGIS, the R summary statistics and histogram scripts worked just fine.

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  • What was your layer source? A zipped set of shapefile files (.shp, .shx, .dbf etc)?
    – Spacedman
    Dec 30, 2015 at 22:44

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