Pwelch and accuracy/number of points

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George Lazaridis
George Lazaridis 2014-7-14
回答： George Lazaridis 2014-7-14
Hello, I have a signal sampled at 200Hz and when I perform the Pwelch method the returning frequency vector is till 100Hz as expected. My interest, though, is only at the frequencies 0-2Hz. Using xlim([0 2]) i can see the frequency content of interest but i want to use more points or maybe downsample my signal in order to get better accuracy at this frequencies. What do you propose?

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Honglei Chen
Honglei Chen 2014-7-14
编辑：Honglei Chen 2014-7-14
If you only need to get more points in pwelch plot, I think increasing the number of FFT points in pwelch should do the trick.

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George Lazaridis
George Lazaridis 2014-7-14
to be more specific, i have derived the HRV signal (the RR intervals) and i want to see the low and hi frequency content. But when i just plot the PSD returned by the Welch's method, i get a different plot than the one expected.

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