Hello all,

I'm sorry if this has been treated before, but I haven't found

anything when searching the archives or the net.

Basically, the problem surfaces when plotting FFT spectras using many

data points. The amplitudes of the peaks in the spectra then seem to

depend on the size of the plot window.

Example code:

from pylab import *

t=arange(65536)

plot(abs(fft(sin(2*pi*.01*t)*blackman(len(t)))))

[<matplotlib.lines.Line2D object at 0x03871990>]

show()

With the original window size (WXAgg backend), I get maximum peaks at

about 390. Zooming in on the peak will increase the amplitude.

Resizing the window can also make the amplitude increase.

The expected amplitude is:

max(abs(fft(sin(2*pi*.01*t)*blackman(len(t)))))

12891.96683092583

Is this a known problem, or should I file a bug report? Is there any

workaround (except decreasing the length of t, and thus the level of

detail)?

I'm using ActivePython 2.6.3.7 for windows, matplotlib 0.99.1 binary,

numpy 1.3.0 and wxPython-unicode-2.8.10.1. I've also tried with the

TkAgg backend, which gives similar results.

Thanks,

Henrik