Merge pull request scipy#5150 from andreas-kopecky/fix_misleading_cwt_example

DOC: fix misleading wavelets/cwt example

Author: Ralf Gommers

scipy/signal/wavelets.py

@@ -350,7 +350,7 @@ def cwt(data, wavelet, widths):
     >>> sig  = np.cos(2 * np.pi * 7 * t) + signal.gausspulse(t - 0.4, fc=2)
     >>> widths = np.arange(1, 31)
     >>> cwtmatr = signal.cwt(sig, signal.ricker, widths)
-    >>> plt.imshow(cwtmatr, extent=[-1, 1, 1, 31], cmap='PRGn', aspect='auto',
+    >>> plt.imshow(cwtmatr, extent=[-1, 1, 31, 1], cmap='PRGn', aspect='auto',
     ...            vmax=abs(cwtmatr).max(), vmin=-abs(cwtmatr).max())
     >>> plt.show()