[Ifeffit] selection of pixels by criteria

I have used larch some for XRF maps. I like the feature for defining ROI's and then looking at the statistics of the data. I have some samples that are an intimate mix of two or more phases and I would like to extract pixels based on a criteria- like high Sr or low Fe, etc, from across a whole map region. I wonder if this feature is available, or would be easy to create on larch? Thanks! E. Troy Rasbury Associate Professor Department of Geosciences Stony Brook University Stony Brook NY 11794 631-632-1488