Hello Yuval, Misha's answer below should solve your question, but I hope you don't mind a comment on the plots you have been doing.
I think there is a better way to go than plotting shifted data MagEdb+40 and then using a deliberately shifted grid to compensate, which is the
RTickLabel = {'-40','-30','-20','-10','0'}
approach from your question of 12 hours or so ago. Plotting the actual data MagEdb followed by
rlim([-40 0])
seems simpler and less error prone. (Your code above does not produce the plot above since the grid shift part is missing).
p.s. it works, but your choice of the variable to call theta seems a bit unconventional.
