Error: "Expected either a logical, char, int, fi, single, or double. Found an mxArray."

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Will Forfang
Will Forfang 2013-2-9
评论： Juan Ramos Zayas 2023-5-4
I have a "Matlab Function" block in simulink containing the following code:
function found = FFTscan( signal, Fs )
PSD=real(fft(signal,2^nextpow2(length(signal)))); %est. power spec density
PSDn=PSD./max(PSD); %normalizes values from FFT
framen=[.0007 .0642 1 .394 .0063]; %frame for XCORR
xcn=xcorr(PSDn,framen); %xcorrelates normalized FFT w/ frame
xcn1 = xcn(((length(xcn)-1)/2):end); %turns 2sided xcorr into 1sided
coder.extrinsic('findpeaks');
[pks, loc] = findpeaks(xcn1,'MINPEAKHEIGHT',.4,'MINPEAKDISTANCE',30);
found=loc.*(Fs/length(signal)); %multiply index by Fs/N to get frequency
The purpose is to take a frame of an incoming signal in the time domain, transform it to the freq domain, then cross-correlate it with a frame of a known signal. This function works fine if I run it in the matlab workspace, but if I try to use it in a simulink model it throws the error mentioned in the title.
How can I use the data in "loc" as output for my simulink block?
Thanks,
-Will
  2 个评论
Walter Roberson
Walter Roberson 2013-2-9
Which line is the problem occurring on? If it is that last line, could you try breaking it up into an assignment to a temporary variable and then on the (new) next line, assign the temporary to "found" ? I am thinking the problem might have to do with the "loc" rather than the "found".
Will Forfang
Will Forfang 2013-2-9
编辑：Will Forfang 2013-2-9
Yes, it's the last line. Do you mean like this?
coder.extrinsic('findpeaks');
[pks, loc] = findpeaks(xcn1,'MINPEAKHEIGHT',.4,'MINPEAKDISTANCE',30);
temp = loc.*(Fs/length(signal)); %multiply index by Fs/N to get frequency
found= temp;
It still outputs the same error. Here's the full error report:
Expected either a logical, char, int, fi, single, or double. Found an mxArray. MxArrays are returned from calls to the MATLAB interpreter and are not supported inside expressions. They may only be used on the right-hand side of assignments and as arguments to extrinsic functions.
Function 'Subsystem1/Algorithm/MATLAB Function' (#76.609.612), line 16, column 8:
"*loc*"
Launch diagnostic report.
I've also tried it this way, and yielded the same error:
temp = loc; %multiply index by Fs/N to get frequency
found= temp.*(Fs/length(signal));
Thanks for your reply,
-Will

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Walter Roberson
Walter Roberson 2013-2-9
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