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97 changes: 42 additions & 55 deletions lib/matplotlib/mlab.py
Original file line number Diff line number Diff line change
Expand Up @@ -1239,78 +1239,65 @@ def specgram(x, NFFT=None, Fs=None, detrend=None, window=None,
"""
Compute a spectrogram.

Call signature::

specgram(x, NFFT=256, Fs=2,detrend=mlab.detrend_none,
window=mlab.window_hanning, noverlap=128,
cmap=None, xextent=None, pad_to=None, sides='default',
scale_by_freq=None, mode='default')

Compute and plot a spectrogram of data in *x*. Data are split into
*NFFT* length segments and the spectrum of each section is
computed. The windowing function *window* is applied to each
Compute and plot a spectrogram of data in x. Data are split into
NFFT length segments and the spectrum of each section is
computed. The windowing function window is applied to each
segment, and the amount of overlap of each segment is
specified with *noverlap*.
specified with noverlap.

*x*: 1-D array or sequence
Array or sequence containing the data
Parameters
----------
x : array_like
1-D array or sequence.

%(Spectral)s

%(PSD)s

*mode*: [ 'default' | 'psd' | 'complex' | 'magnitude'
'angle' | 'phase' ]

What sort of spectrum to use. Default is 'psd'. which takes the
power spectral density. 'complex' returns the complex-valued
frequency spectrum. 'magnitude' returns the magnitude spectrum.
'angle' returns the phase spectrum without unwrapping. 'phase'
returns the phase spectrum with unwrapping.

*noverlap*: integer
The number of points of overlap between blocks. The default value
is 128.

Returns the tuple (*spectrum*, *freqs*, *t*):
noverlap : int, optional
The number of points of overlap between blocks. The default
value is 128.
mode : str, optional
What sort of spectrum to use, default is 'psd'.
'psd'
Returns the power spectral density.

*spectrum*: 2-D array
columns are the periodograms of successive segments
'complex'
Returns the complex-valued frequency spectrum.

*freqs*: 1-D array
The frequencies corresponding to the rows in *spectrum*

*t*: 1-D array
The times corresponding to midpoints of segments (i.e the columns
in *spectrum*).
'magnitude'
Returns the magnitude spectrum.

.. note::
'angle'
Returns the phase spectrum without unwrapping.

*detrend* and *scale_by_freq* only apply when *mode* is set to
'psd'
'phase'
Returns the phase spectrum with unwrapping.

.. seealso::
Returns
-------
spectrum : array_like
2-D array, columns are the periodograms of successive segments.

:func:`psd`
:func:`psd` differs in the default overlap; in returning
the mean of the segment periodograms; and in not returning
times.
freqs : array_like
1-D array, frequencies corresponding to the rows in *spectrum*.

:func:`complex_spectrum`
A single spectrum, similar to having a single segment when
*mode* is 'complex'.
t : array_like
1-D array, the times corresponding to midpoints of segments
(i.e the columns in *spectrum*).

:func:`magnitude_spectrum`
A single spectrum, similar to having a single segment when
*mode* is 'magnitude'.
See Also
--------
psd : differs in the overlap and in the return values.
complex_spectrum : similar, but with complex valued frequencies.
magnitude_spectrum : similar single segment when mode is 'magnitude'.
angle_spectrum : similar to single segment when mode is 'angle'.
phase_spectrum : similar to single segment when mode is 'phase'.

:func:`angle_spectrum`
A single spectrum, similar to having a single segment when
*mode* is 'angle'.
Notes
-----
detrend and scale_by_freq only apply when *mode* is set to 'psd'.

:func:`phase_spectrum`
A single spectrum, similar to having a single segment when
*mode* is 'phase'.
"""
if noverlap is None:
noverlap = 128
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