How can I detect islands in a contour plot?

I am trying to detect abnormalities in data with respect to two variables. (Imagine an smoothly varying image where you are trying to detect anomolies/discrepancies).

I can detect these manually by looking for islands in a contour map, but I can't seem to figure out how to algorithmically detect them. In particular, I am looking for a way to detect embedded islands (e.g. islands within islands).

How can I detect the regions where islands occur? Thanks

Answer 1

[Florin Neacsu]

Hello,

If I didn't misunderstood your problem, I believe the Danielsson algorithm for map distance (CGIP, 14:227–248, 1980) could help you.

Regards, Florin