all points y value undefined! error in gnuplot

Question

i'm trying to plot the following formula using gnuplot, but i get an error message says "all points y value undefined!", what is the problem and what can i do to solve it?

Here is the code:

gnuplot> i = {0.0,1.0}                              
gnuplot>  plot [y=1:100] 1 + (0. + 0.2440625921544017*i)*(0.9680598247711271/y**5 + 0.4600760626004062/y**4 + 0.31009952311074734/y**3 + 0.3289857649601461/y**2 + 0.7029129290126906/y)

Where i is the complex number (Sqrt[-1]).

Seems that your code is not formatted. Edit your question.

user4489658
– user4489658

2016-12-02 13:50:25 +00:00
Commented Dec 2, 2016 at 13:50 — user4489658
– user4489658, Commented Dec 2, 2016 at 13:50
@MichaelO. i edited it.

user42138
– user42138

2016-12-02 14:02:50 +00:00
Commented Dec 2, 2016 at 14:02 — user42138
– user42138, Commented Dec 2, 2016 at 14:02

bibi · Accepted Answer · 2016-12-03 07:44:41Z

1

You cannot directly plot a function with complex values. You must decide which parts of the function you want to plot, use e.g. abs(), imag() or real():

i = {0.0, 1.0}
f(x) = 1 + (0. + 0.2440625921544017*i)*(0.9680598247711271/x**5 + 0.4600760626004062/x**4 + 0.31009952311074734/x**3 + 0.3289857649601461/x**2 + 0.7029129290126906/x)

set xrange [1:10]
plot abs(f(x))

edited Dec 3, 2016 at 7:44

bibi

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answered Dec 2, 2016 at 21:22

Christoph

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1 Comment

Daniel K. Over a year ago

Also helpful is to use arg() for the phase/angle of the complex value, see help arg.

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