plot symbolic function real part

Andrea Giordano (view profile)

on 31 Mar 2019
Latest activity Commented on by Star Strider

on 31 Mar 2019

Star Strider (view profile)

Hello there,
I would like to plot the real part of this symbolic function I have just solved.
Parameters 'a' and 'e' are varying between 5 and 9, and 0.05 and 0.15 respectively.
Unfortunately, it does not work.
Here you go with my code ( solution is a ratio of sum of Bessel functions of order zero).
clc
clear
set(groot,'DefaultAxesFontSize',14)
set(groot,'DefaultLineLineWidth',1.5)
syms a e
A = [besselj(0,-1i*a*e), bessely(0,-1i*a*e); ...
besselj(0,-1i*a), bessely(0,-1i*a)];
b = [-1; -1];
X = linsolve(A, b);
disp(X)
a = linspace(5,9);
e = linspace(0.05, 0.15);
plot(a, e, X)

Star Strider (view profile)

on 31 Mar 2019

You are plotting a function of two variables, so you need to use a plot that accommodates them, and that your function is symbolic.
Try this:
syms a e
A = [besselj(0,-1i*a*e), bessely(0,-1i*a*e); ...
besselj(0,-1i*a), bessely(0,-1i*a)];
b = [-1; -1];
X = linsolve(A, b);
disp(X)
a = linspace(5,9);
e = linspace(0.05, 0.15);
fsurf(real(X), [5 9, 0.05 0.15])
xlabel('a')
ylabel('e')
Experiment to get the result you want.

Andrea Giordano

Andrea Giordano (view profile)

on 31 Mar 2019
Thank you. Any other options that fsurf that I can try?
regards,
Andrea.
Star Strider

Star Strider (view profile)

on 31 Mar 2019
As always, my plesure.
There are several 3D plots that will probably work with your system. See the documentation on fcontour (link), fmesh (link), and fplot3 (link).