Forwarding an email to the devel list, we seem to have an error in mlab.
Dimitris: Please send future issues like this directly to the mailing list or create an issue on GH.
---------- Forwarded message ---------
From: Dimitris Daniel <ddanielwork@…149…>
Date: Thu, Mar 26, 2015 at 4:04 AM
Subject: possible issue with _spectral_helper function in matplotlib/mlab.py when compensate windowing loss
To: <tcaswell@…149…>, <martin.fitzpatrick@…149…>
Dear Mr. Thomas and Mr. Martin,
First of all I would like to thank you for your work.
My name is Dimitris Daniel and I use _spectral_helper in a process.
I think that there is a problem when we try to compensate windowing loss.
You use the row:
result /= (np.abs(windowVals)**2).sum()
However as I can see in Bendat & Piersol Sec 11.5.2. (see attached 3.png) I think the right is something like:
result *= np.sqrt((np.ones(NFFT)**2).sum() / (np.abs(windowVals)**2).sum())
Actually I had some correlation problems with the data from a customer of my for which I build a script for Signal Analysis.
He gave me the input signal and the output he gets from the hardware he is using.
I use some parts from your functions and it was not possible to get the same results.
By changing this row the results are matching together.
Am I missing something or am I right.
Thank you very much for your time and sorry for any inconvenience.
I am looking forward to your response.