.. _pylab_examples-specgram_demo: pylab_examples example code: specgram_demo.py ============================================= .. plot:: /home/mdboom/Work/builds/matplotlib/doc/mpl_examples/pylab_examples/specgram_demo.py :: #!/usr/bin/env python from pylab import * dt = 0.0005 t = arange(0.0, 20.0, dt) s1 = sin(2*pi*100*t) s2 = 2*sin(2*pi*400*t) # create a transient "chirp" mask = where(logical_and(t>10, t<12), 1.0, 0.0) s2 = s2 * mask # add some noise into the mix nse = 0.01*randn(len(t)) x = s1 + s2 + nse # the signal NFFT = 1024 # the length of the windowing segments Fs = int(1.0/dt) # the sampling frequency # Pxx is the segments x freqs array of instantaneous power, freqs is # the frequency vector, bins are the centers of the time bins in which # the power is computed, and im is the matplotlib.image.AxesImage # instance ax1 = subplot(211) plot(t, x) subplot(212, sharex=ax1) Pxx, freqs, bins, im = specgram(x, NFFT=NFFT, Fs=Fs, noverlap=900, cmap=cm.gist_heat) show() Keywords: python, matplotlib, pylab, example, codex (see :ref:`how-to-search-examples`)