How can I plot laplace transformed functions?

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Murloc50 on 28 Nov 2021
Commented: Star Strider on 29 Nov 2021
How can I plot laplace transformed functions? Since the function should be imaginary I can not use fplot, can I? For example, how would I plot this:
syms x
f = sin(x);
l = laplace(f);
Murloc50 on 29 Nov 2021
I think a 3D Plot would be best since it is a function with a complex and real part, wouldnt it? Since I am no expert, what kind of plot would you recommend? Or does this depend on the function laplace() returns?

Star Strider on 29 Nov 2021
It might be easier to do this outside the Symbolic Math Toolbox.
That aside, try this —
syms x s js rs sigma omega
f = sin(x);
l = laplace(f)
l = lc(sigma,omega) = subs(l,{s},{sigma+1j*omega}) % Define As Complex, With Complex Arguments
lc(sigma, omega) = figure
fsurf(lc, [ -0.1 0 -2*pi 2*pi ], 'MeshDensity',125)
xlabel('\sigma')
ylabel('\omega')
set(gca, 'YTick',[-2*pi : pi/2 : 2*pi], 'YTickLabel',compose('%.1f\\pi',(-2:0.5:2)))
axis([-0.1 0.1 -2*pi 2*pi]) Plotting it in two dimensions is of course an option, however the function has three dimensions ( ,amplitude) so a three-dimensional plot is appropriate. The two complex-conjugate poles at are clearly visible.
Not perfect, however the best fsurf can do here with this function!
.
Star Strider on 29 Nov 2021
As always, my pleasure!
.

R2021b

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