Re: [Gnuplot-py-users] Plotting with Gnuplot in Python

[Michael H. <mh...@al...>]

[Please don't send Gnuplot.py emails to me personally.  I am sending a
CC of this response to the correct mailing list.]

Roland deWit wrote:
> When I run the attached script Function1.py in Python I get a plot. 
> However, when I run Function2.py I don't get a plot.  Would you know how
> to fix that?
>
> [Function1.py:]
> import Gnuplot
>
> g = Gnuplot.Gnuplot(debug=1)
> f = Gnuplot.Func('2*x**2')
> g.plot(f)
>
>
> [Function2.py:]
> import Gnuplot
>
> g = Gnuplot.Gnuplot(debug=1)
> a = 2
> f = Gnuplot.Func('a*x**2')
> g.plot(f)

That is because the argument to Func() is passed to gnuplot for
evaluation, and gnuplot knows nothing about the Python variable called "a".

There are two obvious ways to make this work:

g("a = 2") # Assign the *gnuplot* variable "a"
f = Gnuplot.Func('a*x**2')

or

# Interpolate "a" into the function string *before* passing it
# to gnuplot:
f = Gnuplot.Func('%s*x**2' % (a,))

Michael