how "fplot" works?

I have a function which depends on a particular variable, that is T(theta) where the variable is theta. Then, I plotted the function T(theta) with "fplot".

I want to know: which is the frequency of theta with which the fuction T is plotted? I suppose that Matlab consider a lot of theta and compute T for each of these theta.

[dpb]

Just read the documentation...

fplot(f) plots the curve defined by the function y = f(x) over the default interval [-5 5] for x.

It sets the number of points internally; not sure the heuristics it uses but the difference in x-values over a default range isn't identical so it's not just linspace(x1,x2,N). But,it's not trivially obvious just where the algorithm is buried in a very quick look at the m-file.

A trivial plot returned 57 for the number of points in X|YData arrays....interesting choice...

Answer 1

[Ameer Hamza]

fplot does not use fixed mesh spacing. It adaptively calculates the distance between mesh points (probably using derivates) of the function. See the parameter MeshDensity: https://www.mathworks.com/help/releases/R2020a/matlab/ref/fplot.html#bu6xntj-1_sep_shared-MeshDensity. By default, it is 23, but MATLAB usually uses a higher number of points for a smoother curve. The algorithm to adaptively calculate the mesh point is not provided, but you can find out the x-values and y-values of points using the following statements

syms x
y = x.^2*sin(x);
f = fplot(y)
f.XData
f.YData

[Walter Roberson]

Furthermore, fplot has code to attempt to find discontinuities even if they are at a finer spacing than the adaptive mesh would suggest.