Custom FFT Function generates "Insufficient Number of Outputs"

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Artificial_Spark 2017-3-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/328675-custom-fft-function-generates-insufficient-number-of-outputs

编辑： Steven Lord 2017-3-15

Can someone help me determine why l'm getting this message? My Custom FFT Code:

function [X, freq] = centeredFFT(x,Fs)
N = length(x);
if mod(N,2)==0
    k = -N/2:N/2-1;   
else
    k = -(N-1)/2:(N-1)/2;
end
T = N/Fs;
freq = k/T;
X = fft(x)/N;
X = fftshift(X);
end
My Double sided Frequency Spectrum Plot Code:
fo = 2000;
fp = 10000;
Fs = 4000;
Ts = 1/Fs;
t = 0:Ts:1-Ts;
s = (10 + cos(2*pi*fo*t)).*(cos(2*pi*fp*t));
[SfreqDomain,frequencyRange] = centeredFFT(s,Fs);
centeredFFT = figure;
stem(frequencyRange,abs(SfreqDomain));
grid on;
axis(-5,5,0,5);

Thank you for the assistance. Edited for typo.

[SL: edited to apply code formatting]

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David Goodmanson 2017-3-8

Hi Derrick This looks a lot like a case of defining centeredFFT = (something), somewhere in your script. Them Matlab doesn't recognize it as a function anymore and you get that kind of error message. I don't know the intent of the statement

enteredFFT = figure;

and if it is a typo for

centeredFFT = figure;

I would not know the intent of that either. But if the latter statement or something like it got executed, your function dies.

Artificial_Spark 2017-3-8

Yes it was a typo. centeredFFT = figure is to plot the FFT signal.

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Answer 1

Brandon Eidson 2017-3-15

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Hey Derrick, the only error I immediately see in your code is with your use of the "axis" command; you left off the brackets. That line should be as follows.

axis([-5,5,0,5]);

However, I am not sure if there is a case where that would produce the error "insufficient number of outputs". Making the above change allowed me to execute your provided code without error. If after changing the call to "axis" you are still getting an error, please provide more information about your workflow.

David did point out something helpful. The command

centeredFFT = figure;

will create the variable "centeredFFT" and store in it a function handle. But "centeredFFT" is the name of your custom. This type of naming convention is not recommended.