Re: [Matplotlib-users] matplotlib power spectral density (PSD) value discrepancy

[Thomas C. <tca...@gm...>]

What version of mpl are you using? These functions got a lot of work
between 1.3 and 1.4.

I also suspects that there is a normalization issue going on with power vs
power density.

Tom

On Tue, Dec 16, 2014, 22:28 xkryptor <xkr...@gm...> wrote:

> Hi all,
>
>  I tried calculating the power spectral density using matplotlib mlab
> function psd (). I plotted using two methods:
>
>  1. At first I plot it directly using plt.psd (red line in plot)
>  2. Then I output the values from psd() to variables and plotting the
>     variables (blue line in plot)
>
> The code I used:
>
> power, freqs = plt.psd(P * 100000, len(P), Fs = 1 / dt, scale_by_freq=0)
> plt.psd(P * 100000, len(P), 1 / dt, scale_by_freq=0)
> plt.plot(freqs, power)
>
> But the plots are different, I expected it to be coincident. From where
> does the discrepancy arise?
>
> [image: Inline image 1]
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