Revision: 6368
http://matplotlib.svn.sourceforge.net/matplotlib/?rev=6368&view=rev
Author: ryanmay
Date: 2008-11-06 22:53:02 +0000 (Thu, 06 Nov 2008)
Log Message:
-----------
Improve the docstrings for mlab.psd and mlab.csd.
Modified Paths:
--------------
trunk/matplotlib/lib/matplotlib/mlab.py
Modified: trunk/matplotlib/lib/matplotlib/mlab.py
===================================================================
--- trunk/matplotlib/lib/matplotlib/mlab.py 2008-11-05 17:12:03 UTC (rev
6367)
+++ trunk/matplotlib/lib/matplotlib/mlab.py 2008-11-06 22:53:02 UTC (rev
6368)
@@ -238,39 +238,52 @@
a = y.mean() - b*x.mean()
return y - (b*x + a)
-
-
def psd(x, NFFT=256, Fs=2, detrend=detrend_none,
window=window_hanning, noverlap=0):
"""
- The power spectral density by Welches average periodogram method.
- The vector x is divided into NFFT length segments. Each segment
- is detrended by function detrend and windowed by function window.
- noperlap gives the length of the overlap between segments. The
- absolute(fft(segment))**2 of each segment are averaged to compute Pxx,
- with a scaling to correct for power loss due to windowing.
+ The power spectral density by Welch's average periodogram method.
+ The vector *x* is divided into *NFFT* length blocks. Each block
+ is detrended by the function *detrend* and windowed by the function
+ *window*. *noverlap* gives the length of the overlap between blocks.
+ The absolute(fft(block))**2 of each segment are averaged to compute
+ *Pxx*, with a scaling to correct for power loss due to windowing.
- Fs is the sampling frequency (samples per time unit). It is used
- to calculate the Fourier frequencies, freqs, in cycles per time
- unit.
+ If len(*x*) < *NFFT*, it will be zero padded to *NFFT*.
+ *x*
+ Array or sequence containing the data
+
*NFFT*
- The length of the FFT window. Must be even; a power 2 is most
efficient.
+ The number of data points used in each block for the FFT.
+ Must be even; a power 2 is most efficient. The default value is 256.
+ *Fs*
+ The sampling frequency (samples per time unit). It is used
+ to calculate the Fourier frequencies, freqs, in cycles per time
+ unit. The default value is 2.
+
*detrend*
- is a function, unlike in matlab where it is a vector.
+ Any callable function (unlike in matlab where it is a vector).
+ For examples, see :func:`detrend`, :func:`detrend_none`, and
+ :func:`detrend_mean`. The default is :func:`detrend_none`.
*window*
- can be a function or a vector of length NFFT. To create window
- vectors see numpy.blackman, numpy.hamming, numpy.bartlett,
- scipy.signal, scipy.signal.get_window etc.
+ A function or a vector of length *NFFT*. To create window
+ vectors see :func:`window_hanning`, :func:`window_none`,
+ :func:`numpy.blackman`, :func:`numpy.hamming`,
+ :func:`numpy.bartlett`, :func:`scipy.signal`,
+ :func:`scipy.signal.get_window`, etc. The default is
+ :func:`window_hanning`.
- If len(*x*) < *NFFT*, it will be zero padded to *NFFT*.
+ *noverlap*
+ The number of points of overlap between blocks. The default value
+ is 0 (no overlap).
Returns the tuple (*Pxx*, *freqs*).
- Refs: Bendat & Piersol -- Random Data: Analysis and Measurement
Procedures, John Wiley & Sons (1986)
-
+ Refs:
+ Bendat & Piersol -- Random Data: Analysis and Measurement
+ Procedures, John Wiley & Sons (1986)
"""
# I think we could remove this condition without hurting anything.
if NFFT % 2:
@@ -317,26 +330,50 @@
def csd(x, y, NFFT=256, Fs=2, detrend=detrend_none,
window=window_hanning, noverlap=0):
"""
- The cross spectral density Pxy by Welches average periodogram
+ The cross power spectral density by Welch's average periodogram
method. The vectors *x* and *y* are divided into *NFFT* length
- segments. Each segment is detrended by function *detrend* and
- windowed by function *window*. *noverlap* gives the length of the
- overlap between segments. The product of the direct FFTs of *x*
- and *y* are averaged over each segment to compute *Pxy*, with a
- scaling to correct for power loss due to windowing. *Fs* is the
- sampling frequency.
+ blocks. Each block is detrended by the function *detrend* and
+ windowed by the function *window*. *noverlap* gives the length
+ of the overlap between blocks. The product of the direct FFTs
+ of *x* and *y* are averaged over each segment to compute *Pxy*,
+ with a scaling to correct for power loss due to windowing.
- *NFFT* must be even; a power of 2 is most efficient
+ If len(*x*) < *NFFT* or len(*y*) < *NFFT*, they will be zero
+ padded to *NFFT*.
- *window* can be a function or a vector of length *NFFT*. To create
- window vectors see :func:`numpy.blackman`, :func:`numpy.hamming`,
- :func:`numpy.bartlett`, :func:`scipy.signal`,
- :func:`scipy.signal.get_window` etc.
+ *x*, *y*
+ Array or sequence containing the data
- Returns the tuple (*Pxy*, *freqs*)
+ *NFFT*
+ The number of data points used in each block for the FFT.
+ Must be even; a power 2 is most efficient. The default value is 256.
+ *Fs*
+ The sampling frequency (samples per time unit). It is used
+ to calculate the Fourier frequencies, freqs, in cycles per time
+ unit. The default value is 2.
+
+ *detrend*
+ Any callable function (unlike in matlab where it is a vector).
+ For examples, see :func:`detrend`, :func:`detrend_none`, and
+ :func:`detrend_mean`. The default is :func:`detrend_none`.
+
+ *window*
+ A function or a vector of length *NFFT*. To create window
+ vectors see :func:`window_hanning`, :func:`window_none`,
+ :func:`numpy.blackman`, :func:`numpy.hamming`,
+ :func:`numpy.bartlett`, :func:`scipy.signal`,
+ :func:`scipy.signal.get_window`, etc. The default is
+ :func:`window_hanning`.
+
+ *noverlap*
+ The number of points of overlap between blocks. The default value
+ is 0 (no overlap).
+
+ Returns the tuple (*Pxy*, *freqs*).
+
Refs:
- Bendat & Piersol -- Random Data: Analysis and Measurement
+ Bendat & Piersol -- Random Data: Analysis and Measurement
Procedures, John Wiley & Sons (1986)
"""
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