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Warning: Integer operands are required for colon operator when used as index

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I am using fft functions and have twice in my code this warning message, bu no clue why I get the warning:
N = 2048*16;
sizeData = size(data,2);
padding = (N-sizeData)/2;
cInput = zeros([1 N]); % <-- Warning
cInput(padding+1:(padding+sizeData)) = data;
cInput = fftshift(cInput);
% transform
cfourier = fftshift(fft(cInput));
% iFFt
cOutput = ifft(ifftshift(cfourier));
cOutput = ifftshift(cOutput); % <-- Warning
AmpIFourier = abs(cOutput(padding+1:(padding+sizeData)));

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Accepted Answer

Image Analyst
Image Analyst on 20 Feb 2012
(N-sizeData)/2 can be a fractional number, e.g. "something point 5" so try
padding = floor((N-sizeData)/2);
or better yet, just use the padarray() function to do your padding.

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Matthias Pospiech
Matthias Pospiech on 21 Feb 2012
The line number really are the ones that I marked. So do not blame me, blame matlab.
Jan
Jan on 21 Feb 2012
@Matthias: I've never seen a bug in Matlab, which leads to a wrong line number for warnings. While I assume IA and Oleg point to the correct solution, there must be an additional problem.
Hannetjie
Hannetjie on 6 Mar 2015
@Jan Simon: It is now 3 years later so my apologies if this has since been touched upon in newer posts... But I came across this same anomaly (and this is the first and only time I've seen it). When running my code through, I get
Warning: Integer operands are required for colon operator when used as index > In tdnoise3 at 73
The warning in my case makes no sense at line nr 73. However, if I step through the exact same code, I get
Warning: Integer operands are required for colon operator when used as index > In tdnoise3 at 81
Which does make sense and was where the fix was required.
But OK, has no bearing on the topic of this post.

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More Answers (2)

Oleg Komarov
Oleg Komarov on 20 Feb 2012
Perfectly fine
idx = 2.5:9;
But when you use to index a position:
A = rand(10,1);
A(idx)
There's no such a thing as position number 2.5

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Jan
Jan on 20 Feb 2012
N = 2048*16;
cInput = zeros([1 N]); % <-- Warning
No, I do not get a warning in this code. Are you sure, that this is the original code?

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