Set defaults for NFFT and noverlap function wide in _axes.specgram() …

…and mlab.specgram().
matplotlib · efiring · Jan 17, 2017 · Jan 16, 2017 · Jan 16, 2017 · Jan 16, 2017
commit 37481ad842cf46317e18ef0d0deae834fd4af890
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -7200,8 +7200,12 @@ def specgram(self, x, NFFT=None, Fs=None, Fc=None, detrend=None,
        if not self._hold:
            self.cla()

+        if NFFT is None:
+            NFFT = 256  # same default as in mlab.specgram()
        if Fc is None:
-            Fc = 0
+            Fc = 0  # same default as in mlab._spectral_helper()
+        if noverlap is None:
+            noverlap = 128  # same default as in mlab.specgram()

        if mode == 'complex':
            raise ValueError('Cannot plot a complex specgram')
@@ -7234,11 +7238,6 @@ def specgram(self, x, NFFT=None, Fs=None, Fc=None, detrend=None,
        Z = np.flipud(Z)

        if xextent is None:
-            # define default values:
-            if noverlap is None:
-                noverlap = 128  # defined in mlab.specgram
-            if NFFT is None:
-                NFFT = 256  # defined in mlab._spectral_helper
            # padding is needed for first and last segment:
            pad_xextent = (NFFT-noverlap) / Fs / 2
            xextent = np.min(t) - pad_xextent, np.max(t) + pad_xextent

diff --git a/lib/matplotlib/mlab.py b/lib/matplotlib/mlab.py
@@ -1273,8 +1273,10 @@ def specgram(x, NFFT=None, Fs=None, detrend=None, window=None,

    """
    if noverlap is None:
-        noverlap = 128
-    if len(x) <= (256 if NFFT is None else NFFT):  # see _spectral_helper()
+        noverlap = 128  # default in _spectral_helper() is noverlap = 0
+    if NFFT is None:
+        NFFT = 256  # same default as in _spectral_helper()
+    if len(x) <= NFFT:
        warnings.warn("Only one segment is calculated since parameter NFFT " +
                      "(=%d) >= signal length (=%d)." % (NFFT, len(x)))