Could you add an example that display the Gutemberg relation: Log(N) = a - b M?

hi dear developer,
Could you please add an example that display the Gutemberg relation: Log(N) = a - b M?
At present, I have no good data attached.


This example has no horizontal segments in the Gutemberg relation.
Thank you very much.

Sort of looks correct (is this GMT 3 or 4 syntax?)
What is going wrong? Is the socal.trend file not doing what you expected? hard to check without test data or knowing what is wrong.