I tried switching off some titles by substituting the command 'title' with 'notitle', but this seems to fail when the title is generated by a function:
mytitle(n) = 'my test title nr '.n
plot x title mytitle(1)
plot x notitle mytitle(1)
On Ubuntu 12.04, gnuplot 4.6.4 says to the 2nd plot command
and cvs head
unexpected or unrecognized token
When 'mytitle' is a simple string constant, there is no problem.