In reply to Joe M.

Nice, thanks for sharing. I haven't plotted robust statistics myself, but what you report makes sense. Each of the curves/regions in the moment-ratio diagram are the image of a function. The domain of the function is the space of parameters for a family of distributions. The range for the conventional M-R diagram is the image of (skew(p), kurt(p)), where p is a vector of the parameters for the family. If you change the mapping by using different statistics (including robust statistics), the location of the curves will be different, but the idea is the same. I have also seen this kind of diagram for the coefficient of variation versus the skewness.