Thanks! That fixed it! -Noah On Wed, Mar 8, 2023 at 5:40 PM Sarah Goslee <sarah.gos...@gmail.com> wrote:
> Hi Noah, > > It appears to be the same problem as this: [reading rasters in r using > terra package]( > https://gis.stackexchange.com/questions/398061/reading-rasters-in-r-using-terra-package > ). > As in that question, adding 0 forces the conversion, but loses all the > information about color table, etc. > > canopy <- rast('nlcd_2016_treecanopy_2019_08_31.img', lyrs=1) > > c2 <- canopy + 0 > > > c2 > 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 : spat_t0Rj6gEgi2CzsAZ_16778.tif > name : Histogram > min value : 0 > max value : 255 > > I didn't try the devel version of terra, though. > > Sarah > > On Wed, Mar 8, 2023 at 6:17 AM Noah Charney <noah.char...@maine.edu> > wrote: > > > > 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 > > > > -- > Sarah Goslee (she/her) > http://www.numberwright.com > [[alternative HTML version deleted]] _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
