问题
I'm trying to save a raster in R, which was cropped from GLC2000. The resulting raster has 4390 rows and 4390 cols, covering Brazil and part of South America. The command to save it (as a GeoTIFF) is either
writeRaster(r1,'Raster1.tif')
or
writeRaster(r1,'Raster1.tif','GTiff')
Both keep trying to save the file for several hours, but they don't even create the file, much less finish the write process.
I doubt that's because of the size of the file (I think the file should at least start saving, with a temporary file appearing, visible or hidden -- none exists). Two other similar TIFF files (almost the same area, though all South America except Brazil is black) have 2.7 MB (indexed, gives errors when opening on Gimp: "Unknown field with tag 33550 (0x830e) encountered", and other tags) and 19.3 MB (also indexed, gives no errors on Gimp).
I don't think it's because of directory permissions, because R could save the script in the same directory (the permissions are drwxr-xr-x, and I'm the owner and the group owner).
There are 11.6 GB available in the specified file system.
I'm using Debian Jessie 64-bit with Gnome 3.14.1, and R 3.3.3 with RStudio 1.0.136.
My processor is a Intel® Core™ i3-6100 CPU @ 3.70GHz × 4, with 7.8 GiB RAM.
Should writeRaster take so long to save a raster which is not even that big? What may be going wrong?
EDIT
So I'm trying with smaller sizes.
ext <- extent(-67,-65,-1,1)
r1 <- crop(r,ext)
dim(r1) # 224 224 1
writeRaster(r1,'Raster1','GTiff') # works
ext <- extent(-68,-64,-2,2)
r1 <- crop(r,ext)
dim(r1) # 448 448 1
writeRaster(r1,'Raster2','GTiff') # works
ext <- extent(-69,-63,-3,3)
r1 <- crop(r,ext)
#Warning message:
#In .getRat(x, ratvalues, ratnames, rattypes) : NAs introduced by coercion
dim(r1) # 672 672 1
writeRaster(r1,'Raster3','GTiff') # takes forever
Looks like the error is the NAs being introduced by coercion, this prevents the file from being saved. I've tried
r1[is.na(r1)] <- 0
But still the file won't be saved. Why in the world would crop introduce NAs to a common raster, if I'm cropping inside the limits of the raster?
extent(r)
# class : Extent
# xmin : -180.0045
# xmax : 179.9955
# ymin : -56.01339
# ymax : 89.99554
EDIT 2
> levels(r)
[[1]]
ID COUNT CLASSNAMES
1 1 12875179 Tree Cover, broadleaved, evergreen
2 2 8688097 Tree Cover, broadleaved, deciduous, closed
3 3 4099003 Tree Cover, broadleaved, deciduous, open
4 4 15080165 Tree Cover, needle-leaved, evergreen
5 5 8054159 Tree Cover, needle-leaved, deciduous
6 6 5606446 Tree Cover, mixed leaf type
7 7 579763 Tree Cover, regularly flooded, fresh water
8 8 115705 Tree Cover, regularly flooded, saline water
9 9 4269938 Mosaic: Tree Cover / Other natural vegetation
10 10 587270 Tree Cover, burnt
11 11 3195387 Shrub Cover, closed-open, evergreen
12 12 15605651 Shrub Cover, closed-open, deciduous
13 13 17560702 Herbaceous Cover, closed-open
14 14 23573022 Sparse herbaceous or sparse shrub cover
15 15 3089962 Regularly flooded shrub and/or herbaceous cover
16 16 21692769 Cultivated and managed areas
17 17 4025653 Mosaic: Cropland / Tree Cover / Other natural vegetation
18 18 3921904 Mosaic: Cropland / Shrub and/or grass cover
19 19 24629888 Bare Areas
20 20 471034157 Water Bodies
21 21 10660085 Snow and Ice
22 22 378999 Artificial surfaces and associated areas
23 23 29056 No Data
See also this related question.
回答1:
As by discussion in comments, the error message indicated something wrong happening with the Raster Attribute Table. The problem could be related with special characters or length of the labels. As soon as an "offending label" is brought in by the subsetting, you start having problems.
Simplifying the classnames using
levels(r)[[1]]$CLASSNAMES <- letters[1:23]
solved the issue.
Looking at this related question Why is crop introducing NAs to my raster? showed that the problem was in having semicolumns (:) in the names of the classes, which somehow led to "splitting" the class names while cropping.
来源：https://stackoverflow.com/questions/46823110/why-wont-writeraster-save-a-4390x4390-raster