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POMask raster from data in shapefile
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copied!<p>I am trying to standardise a raster file by removing the values exceeding the mean +/- 2.5 std calculated for each polygon of a shapefile. I manage to calculate the zonal statistics and feed them back into the shapefile, but am unable to mask my raster file with the data included in the shapefile. I get an error message running the last two lines of code. Extracting the values above mean + 2.5 std gives me only a value (NA), rather than a raster as output and as a result the mask function gives the following error: </p> <p>Error in (function (classes, fdef, mtable): unable to find an inherited method for function ‘mask’ for signature ‘"RasterBrick", "logical"’</p> <pre><code>#Read raster file library(raster) prec <- getData('worldclim', var='prec', res=10) #Read shapefile france <- getData('GADM', country='FRA', level=1) #Convert shapefile to raster r_fra <- rasterize(france, prec) #Calculate mean for each polygon mean_fra_prec <- zonal(prec, r_fra, FUN='mean') #Calculate standard deviation for each polygon std_fra_prec <- zonal(prec, r_fra, FUN = 'sd') #Calculate mean +/- 2.5 std for each polygon ul_prec <- mean_fra_prec + (2.5 * std_fra_prec) ll_prec <- mean_fra_prec - (2.5*std_fra_prec) #Merge mean +/- 2.5 std for each polygon x <- data.frame(zone=1:22) ul_prec2 <- merge(x, ul_prec, by='zone', all.x=TRUE) ll_prec2 <- merge(x, ul_prec, by='zone', all.x=TRUE) #Join new data to shapefile france@data <- cbind(france@data, ul_prec2[,-1]) france@data <- cbind(france@data, ll_prec2[,-1]) #Remove values above mean + 2.5 std for each polygon ext_prec <- prec[!(prec > france@data$ul_prec2)] <- NA #Values above mean + 2.5 std ma_prec <- mask(prec, ext_prec) #Mask values above mean + 2.5 std </code></pre>

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