Dear r-helpers, I want to randomly sample n points from regions of a raster layers, the cells denoted as "NA" is not included in this sampling process. And, I want to got the longitude and latitude of the sampled points. I checked the manual of raster package, I found several functions is relative to my purpose. I tried them all, but I failed. Can it can be done by raster functionalities. Could you please refer me to the right direction? I expect to hearing from you. Your helps are very valuable for a Chinese who can not reach helps nearby. Best, Sincerely, Mao Jian-Feng