How to define a function without arguments in gnuplot?

Question

I want to define a function which returns a random number:

gnuplot> rnd() = int(rand(0)*2**24)
         ^
         invalid command

I need add a parameter x to stop the error message:

gnuplot> rnd(x) = int(rand(0)*2**24)

Is it possible to define a function without parameters?

mgilson · Accepted Answer · 2012-06-02 12:05:51Z

3

I don't think that is possible (look at the syntax for functions in help user-defined). As far as I can tell -- using rand is the only time when this is useful -- In all other cases your "function" would just evaluate to a constant. I'm guessing the gnuplot devs just haven't thought of this (interesting) corner case, or they didn't think it useful enough to implement.

I hope that I'm wrong about this and somebody else comes along and proves it, but I don't think I am. I think the easiest workaround it to just pass a parameter as you've already mentioned. If you really don't like that, you could use a macro:

set macro
rnd="(int(rand(0)*2**24))"
print 5+@rnd

answered Jun 2, 2012 at 12:05

mgilson

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1 Comment

Joseph Quinsey Over a year ago

You said "rand is the only time when this is useful". I often write functions with a dummy parameter. These will eventually invoke something like column(42).

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