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2012 Mar 05
1
Error in file(fname, "r") : invalid 'description' argument when running maptools' readAsciiGrid on a dataframe
...I'm trying to calculate a sum of differences between two ascii grids. I have the file names of the two grid files in a data.frame along with other data. I'm then trying to add a new column to the data.frame with the result of that calculation. eg. library(maptools) difcount <- function(surfA, surfB) { A <- readAsciiGrid(surfA, colname="a") B <- readAsciiGrid(surfB, colname="b") sum(A$a - B$b) } attach(mydataframe) difcount(surfA[1],surfB[1]) #this test part works fine and gives me the correct result #But when I try to do a batch job by running the funct...