Hello, I have an Ascii grid that was created using the GridAscii command in ArcGrid. The grid represents cell distance to railroads and has values ranging from 0 to 37,082. When I bring this grid into R as a SpatialGridDataFrame, the maximum and/or the minimum values in the grid do not exactly match the original grid. I have tried using both readGDAL and readAsciiGrid for this purpose. I have confirmed in a text editor that the Ascii file does contain the maximum value of 37,082. Below are the results I have seen. Note the differences in the Max. value and Min. value (from readGDAL).
> g1 <- readAsciiGrid("G:/Oconto/WI_Fire/distrail_100m.asc") > summary(g1) Object of class SpatialGridDataFrame Coordinates: min max coords.x1 -263487.6 149512.4 coords.x2 358821.1 666821.1 Is projected: NA proj4string : [NA] Number of points: 2 Grid attributes: cellcentre.offset cellsize cells.dim 1 -263437.6 100 4130 2 358871.1 100 3080 Data attributes: Min. 1st Qu. Median Mean 3rd Qu. Max. NA's 0 2878 6562 7896 11670 37080 6483714 > g2 <- readGDAL("G:/Oconto/WI_Fire/distrail_100m.asc") G:/Oconto/WI_Fire/distrail_100m.asc has GDAL driver AAIGrid and has 3080 rows and 4130 columns > summary(g2) Object of class SpatialGridDataFrame Coordinates: min max x -263487.6 149512.4 y 358821.1 666821.1 Is projected: NA proj4string : [NA] Number of points: 2 Grid attributes: cellcentre.offset cellsize cells.dim x -263437.6 100 4130 y 358871.1 100 3080 Data attributes: Min. 1st Qu. Median Mean 3rd Qu. Max. NA's -32770 2844 6516 7718 11600 32770 6483714 The results from readAsciiGrid are pretty close (Max = 37,080) to the original grid, but readGDAL results in much different values. I would expect both functions to create an object with exactly the same values as the Ascii grid. Can anyone explain why this occurs, and if there is a different way to get my grid into R (I eventually need an 'im' to work with)? I am new to spatial analysis using R, so if there is something obvious I am missing I apologize. Thanks in advance for any help! Cheers, -Brian ======================= Brian R. Miranda USDA Forest Service Northern Research Station brmira...@fs.fed.us Institute for Applied Ecosystem Studies 5985 Highway K Rhinelander, WI 54501 phone: 715-362-1186 fax: 715-362-1166 [[alternative HTML version deleted]] _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo