Problem with matrix as input for pwelch()
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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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Answers (2)
Image Analyst
on 13 Feb 2016
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?
2 Comments
Image Analyst
on 14 Feb 2016
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
on 14 Feb 2016
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.
Honglei Chen
on 16 Feb 2016
Hi Jan, can you run
which pwelch
and see if you are indeed running the correct pwelch? Also it will be helpful if you could share which release your MATLAB is.
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