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

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Rex Cheang
Rex Cheang 2021-8-25
回答： Cris LaPierre 2021-8-25
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?

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采纳的回答

Cris LaPierre
Cris LaPierre 2021-8-25
Ran in:
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)

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