extract() function to get remote sensing image cell value.The same code to process tif file produce error message. Code as follows：
r1 <- raster("2000_2605_1.1_km_monthly_NDVI.tif") polygon_mus <- extent(c(107, 111, 37, 40)) cell <- extract(r1, polygon_mus)
This *.tif is a output file from MODI hdf file with MRT. The process result is as follow:
Error in (function (classes, fdef, mtable) : unable to find an inherited method for function extent?for signature ?NULL"?
Where is the error? I seem to be missing it.