Gnuplot: Plotting different functions in a loop

Question

I'd like to plot the Hermite polynomials in the same graph without having to type them one by one using a loop. I've tried something like this:

    H0(x) = 1 
    H1(x) = 2*x 
    H2(x) = 4*x*x-2 
    H3(x) = 8*x**3-12*x 
    H4(x) = 16*x**4-48*x**2+12 
    H5(x) = 32*x**5-160*x**3+120*x

    plot for[i=0:5] H.i(x)

but It won't work, it'll say: undefined variable: H. I've seen the variable i can be used as a string but I haven't been able to find if there's a way to use it as a string when calling a function.

Miguel · Accepted Answer · 2015-05-17 18:39:22Z

3

Try a different approach, including the index i as an argument of the function:

H(i,x) = (i == 0 ? 1 : \
          i == 1 ? 2*x : \
          i == 2 ? 4*x*x-2 : \
          i == 3 ? 8*x**3-12*x : \
          i == 4 ? 16*x**4-48*x**2+12 : \
          i == 5 ? 32*x**5-160*x**3+120*x : 1/0)

plot for[i=0:5] H(i,x)

enter image description here

answered May 17, 2015 at 18:39

Miguel

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Comments

ROBERTO TOSCANO FLETES · Accepted Answer · 2019-03-13 19:40:59Z

0

An improvement can be

set term wxt persist

set xrange[-1:1]

H(i,x) = (i == 0 ? 1 : \
      i == 1 ? 2*x : \
      i == 2 ? 4*x*x-2 : \
      i == 3 ? 8*x**3-12*x : \
      i == 4 ? 16*x**4-48*x**2+12 : \
      i == 5 ? 32*x**5-160*x**3+120*x : 1/0)

plot for[i=0:5] H(i,x) title sprintf("H(").sprintf('%d',i).sprintf(",x)")

Hermite

enter image description here

edited Mar 13, 2019 at 19:40

answered Mar 11, 2019 at 18:22

ROBERTO TOSCANO FLETES

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4 Comments

U. Windl Over a year ago

The original question did not have xrange specified, so your answer also should not (unless its required to work). Maybe edit your answer.

Miguel Over a year ago

Using string concatenation with the . operator defeats the purpose of using sprintf(). Also, I don't see how this is an "improvement".

ROBERTO TOSCANO FLETES Over a year ago

I do not care about your comments

U. Windl Over a year ago

So you copied another answer, added little extra quality and don't care about comments? I suggest to delete this answer.

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