I want to run statistical band correlation of an image in ENVI. The image has been masked with polygon of interest, and shows no-data value outside the polygon. I expected that it calculated only the masked area. In fact it calculated all pixel in rectangular image. The correlation result of the masked image is the same with that of rectangular image. Also it reported the minimum pixel as 0, while it is no 0 value in in the masked image. It will be very pleased If some one could help me, how to make a real masking in ENVI.