Cannot plot the fourier function "ERROR Data must be numeric, datetime, duration or an array convertible to double"

clear all

close all

%Sampling time

Ts=0.001;

t=0:Ts:2*pi;

%Timeaxis

TimeAxes_x = [0 10 0 0.5];

TimeAxes_y = [0 100 0 5000];

%Inverse fourier transform

syms w;

F2 = 1/(1+w^2);

f2 = ifourier(F2,t);

%F2w = 1/(1+t);

%Sampling frequency

fs=1/Ts;

w=(0:length(f2)-1)*fs/length(f2);

graph_subplot(1,211,w,abs(F2),TimeAxes_x,'t(s)','f2(w)','Frequency Doman of f2(t)');

Basically it just tells me that "ERROR Data must be numeric, datetime, duration or an array convertible to double" for that graph_subplot function. That function is basically a plot function. It mainly happens becasue of the w and abs(F2) in the functon. Can someone please help me with this?

[Cris LaPierre]

You have not shared your function graph_subplot.

Answer 1

[Cris LaPierre]

F2 is a symbolic expression, not numeric. You need to either substitute in values for the symbolic variable w, or use a method for plotting that supports symbolic expressions (e.g. fplot).

You cannot just assign a value to w. That just overwrites the symbolic variable. Try using subs.

%Sampling time
Ts=0.001;
t=0:Ts:2*pi;
%Inverse fourier transform
syms w;
F2 = 1/(1+w^2);
f2 = ifourier(F2,t);
%Sampling frequency
fs=1/Ts;
w2=(0:length(f2)-1)*fs/length(f2);

% substitute
plot(w2,abs(subs(F2,w,w2)))

% fplot
figure
fplot(F2)