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Topic: combining two separate PSD plot
Replies: 1   Last Post: Jun 13, 2013 4:06 PM

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Derek Goring

Posts: 3,922
Registered: 12/7/04
Re: combining two separate PSD plot
Posted: Jun 13, 2013 4:06 PM
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On Friday, June 14, 2013 1:57:11 AM UTC+12, Karthick Selvam wrote:
> Hello,
> I am trying to plot PSD for my temperature data. There were a total of 90000 rows(90000*1) of temperature data in my csv file. When I did the fft of temperature data I decided to divide my data into two parts(Part1-data from (1:65536) and Part2- data from (58232:91000) )and did two separate PSDs. Now I do not know how to combine them as I am new to doing PSD. Can anybody please guide me as to how to do it and comment if what I am trying to do is correct? Thank you for your help in advance.

You can't.
They are different lengths and have different frequencies.
Usually, what we do is to divide the signal into a number of ensembles of equal length, calculate the PSD of each, then find the mean - this is called ensemble averaging. It's one way to smooth the spectrum.
So, in answer to your question: what you're doing is NOT correct.

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