Gnuplot: unset variable

Question

Quite a basic question, I guess, but neither Google nor the docs helped me much so: is it possible to undefine variables? So that

a = 0
[some operation]
print(exists("a"))

results in 0 being printed.

Answer 1

What you are looking for is undefine:

gnuplot> print a           
         undefined variable: a

gnuplot> print(exists("a"))
0
gnuplot> a=10
gnuplot> print a           
10
gnuplot> print(exists("a"))
1
gnuplot> undefine a
gnuplot> print a           
         undefined variable: a

gnuplot> print(exists("a"))
0
gnuplot>