Multiple errors with an integral

12 次查看（过去 30 天）
Reymi Chacon
Reymi Chacon 2018-2-24
评论： Walter Roberson 2022-1-6
I am trying to find the energy of a signal in the frequency domain, but I am having trouble with the integral. I have had multiple errors which is why I did not choose one for the title. Some are: "Undefined function 'abs' for input arguments of type 'function_handle'", Error using integralCalc (...)set the 'ArrayValued' option to true..",etc.
This is the code:
clc
Fs=33280;
t = 0:1/Fs:(N/Fs)-(1/Fs);
N = 256;
x = 4*sin(1040*pi*t) + cos(3120*pi*t);
w = (-2*pi*Fs)/2:(2*pi*Fs)/N:(2*pi*Fs)/2-(2*pi*Fs)/N;
X =@(w) 1/N*fftshift(fft(x));
Px = integral((abs(X)).^2,-inf,inf);
disp(Px)
The error says: Undefined function 'abs' for input arguments of type 'function_handle'.
x is the signal in time, and X is the signal in the domain of frequency after Fourier.

请先登录，再回答此问题。

采纳的回答

Steven Lord
Steven Lord 2018-2-24
The abs function is not defined for function handles. You will need to create a new function handle that evaluates your original function handle and takes the abs of the values it returns:
absX = @(w) abs(X(w));
Now take the integral of absX instead of X.
  3 个评论
显示 1更早的评论
Walter Roberson
Walter Roberson 2018-2-24
You removed the @(w) from your definition of X. You still need a @()
X =@(x) 1/N*fftshift(fft(x));
It is not clear how your vector, w, of 256 (N) points, fits into all of this.
It looks to me as if w is intended to be your signal and that you are asked to calculate its energy. integral() is for calculating integrals of functions (or formulae) and you do not appear to have a function here. It appears to me that you should be doing a numeric integration such as by using trapz()
Reymi Chacon
Reymi Chacon 2018-2-24
Ah thank you. It seems trapz works without problems.

请先登录，再进行评论。

更多回答（1 个）

nassima el ouarie
please help me why the integration function is not working i don't know why ??
i want to compute this integral but this is what ti gives me matlab :
Error in integral (line 88)
Q = integralCalc(fun,a,b,opstruct);
Error in JENERALANDA (line 12)
JG1=integral(f,L1,L2);
this is the function i wrote to compute the integral :
function [JGL] = JENERALANDA()
syms L;
q=1.602176620*10^(-19);
Lw=(90*10^(-9));
w=(900*10^(-9));
N=50;
B=changalphaB();
Z=changalphaW();
L1=(0.24*10^(-6));
L2=(1.08*10^(-6));
f=@(L) ((2.3*10^(18)).*(1-exp(-B.*w-Z.*N.*Lw)));
JG1=integral(f,L1,L2);
JGL=-(q.*(JG1));
end
  1 个评论
Walter Roberson
Walter Roberson 2022-1-6
f=@(L) ((2.3*10^(18)).*(1-exp(-B.*w-Z.*N.*Lw)));
That does not use L, so no matter what the input it always returns the same output.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Numerical Integration and Differentiation 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by