Problem with matrix as input for pwelch()

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Jan Pastyka 2016-2-13

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https://ww2.mathworks.cn/matlabcentral/answers/268020-problem-with-matrix-as-input-for-pwelch

评论： Jan Pastyka 2016-2-17

I am trying to use pwelch fuction, but when I put in data in matrix (columns are independent parts of signal). pwelch returns PSD only for first column (vector), but I expected matrix with PSD in columns for every culomn. What I do wrong? My code is:

x; % data in matrix
w = pwelch(x); % w is vector with PSD of first column of x

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Answer 1

Image Analyst 2016-2-13

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https://ww2.mathworks.cn/matlabcentral/answers/268020-problem-with-matrix-as-input-for-pwelch#answer_209727

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Strange. Run this code and then paste the results in the command window back here:

clc;
x = rand(1000, 10);
whos x
spectra = pwelch(x);
whos spectra
message = sprintf('pwelch(data) returned %d spectra', size(spectra, 2))
uiwait(helpdlg(message));

What do you observe?

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Image Analyst 2016-2-14

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Jan's response to me moved here because it's not an answer to her original question at the top:

My result:

Name         Size            Bytes  Class     Attributes
x         1000x10            80000  double              
Name           Size            Bytes  Class     Attributes
spectra      129x1              1032  double              
message =
pwelch(data) returned 1 spectra

so I think it still doesn't work. And I use Matlab 2013a if it can have some effect...

Image Analyst 2016-2-14

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Jan, you should get this:

    Name         Size    Bytes  Class     Attributes
    x         1000x10    80000  double              
    Name         Size    Bytes  Class     Attributes
    spectra    129x10    10320  double              
message =
pwelch(data) returned 10 spectra

You didn't name some other function pwelch(), did you? What does this say

>> which -all pwelch

If it doesn't say this:

C:\Program Files\MATLAB\R2015b\toolbox\signal\signal\pwelch.m

and lists two files instead, then you'll have to get rid of the other file or rename it. If it does say that, then call the Mathworks to help you investigate it further.

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