How is it possible to identify quickly (without doing many tests) an approximative number of clusters from a dataset which is not vary large, even if this value is not the correct number of clusters, I just want to identify a reasonable value representing the number of clusters from this small dataset.
Note1: that I don't want to do many tests and/or cross-validate just to find an optimal number of clusters (time is important for me).
Note2: I know that there is no way to automatically set the "right" K nor is there a definition of what "right" is. I just want a reasonably approximative value.