Hi, Can someone tell me what I'm missing? I can't get the rast() function in terra to return the actual cell values from an .img file, it just keeps giving strange histogram values. The plot() looks ok, except the legend has those same useless values. Similarly on the categorical NLCD Land Cover layer it gives me data associated with each cell value (e.g. land cover type), which is fine to work with, but still not the actual cell values as I'd expect. The old raster() function in raster package works fine (see below). Thanks for insights! -Noah
> #Download Tree Canopy Layer from NLCD > # https://www.mrlc.gov/data/nlcd-2016-usfs-tree-canopy-cover-conus > > #terra package gives me nonsensical histogram values > library(terra) > canopy <- rast('D:/GIS/Land Cover/nlcd_2016_treecanopy_2019_08_31/nlcd_2016_treecanopy_2019_08_31.img') > canopy class : SpatRaster dimensions : 104424, 161190, 1 (nrow, ncol, nlyr) resolution : 30, 30 (x, y) extent : -2493045, 2342655, 177285, 3310005 (xmin, xmax, ymin, ymax) coord. ref. : Albers Conical Equal Area source : nlcd_2016_treecanopy_2019_08_31.img color table : 1 categories : Histogram, Red, Green, Blue name : Histogram min value : 5737352684 max value : 7854320129 > plot(canopy) > canopy[50000,50000] Histogram 1 24314964 > extract(canopy,data.frame(x=1000000,y=1000000)) ID Histogram 1 1 44832754 > > #raster package works fine > library(raster) > canopy <- raster('D:/GIS/Land Cover/nlcd_2016_treecanopy_2019_08_31/nlcd_2016_treecanopy_2019_08_31.img') > canopy class : RasterLayer dimensions : 104424, 161190, 16832104560 (nrow, ncol, ncell) resolution : 30, 30 (x, y) extent : -2493045, 2342655, 177285, 3310005 (xmin, xmax, ymin, ymax) crs : +proj=aea +lat_0=23 +lon_0=-96 +lat_1=29.5 +lat_2=45.5 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs source : nlcd_2016_treecanopy_2019_08_31.img names : Histogram values : 0, 255 (min, max) attributes : ID Histogram Red Green Blue from: 0 5737352684 255 255 255 to : 255 7854320129 255 255 255 > canopy[50000,50000] 24 > extract(canopy,data.frame(x=1000000,y=1000000)) 94 > > #Land Cover (categorical) layer gives associated categories (not values) in terra > # https://www.mrlc.gov/data/nlcd-2019-land-cover-conus > > nlcd <- rast('D:/GIS/Land Cover/nlcd_2019_land_cover_l48_20210604/nlcd_2019_land_cover_l48_20210604.img') > nlcd class : SpatRaster dimensions : 104424, 161190, 1 (nrow, ncol, nlyr) resolution : 30, 30 (x, y) extent : -2493045, 2342655, 177285, 3310005 (xmin, xmax, ymin, ymax) coord. ref. : Albers Conical Equal Area source : nlcd_2019_land_cover_l48_20210604.img color table : 1 categories : NLCD Land Cover Class, Histogram, Red, Green, Blue, Opacity name : NLCD Land Cover Class min value : Unclassified max value : Emergent Herbaceous Wetlands > nlcd[50000,50000] NLCD Land Cover Class 1 Evergreen Forest > extract(nlcd,data.frame(x=1000000,y=1000000)) ID NLCD Land Cover Class 1 1 Evergreen Forest > ~~~ Dr. Noah Charney (he/him) Assistant Professor of Conservation Biology Department of Wildlife, Fisheries, and Conservation Biology University of Maine, Orono, ME 230 Nutting Hall (207) 581-1284 [[alternative HTML version deleted]] _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
