With no indication of what P and x really are, a couple of choices come to mind...
a) have each script now write its output to disk (a .mat file is particularly simple) with a specific name to not overwrite the other and then write a third script that reads the two files and does the plotting, or
b) write a top level function that calls the two scripts which you convert into functions that return their computed results.
More detail on the form could allow more specificity in the response but the general idea should be clear...
