Revision: 6648
http://matplotlib.svn.sourceforge.net/matplotlib/?rev=6648&view=rev
Author: jdh2358
Date: 2008-12-17 14:57:28 +0000 (Wed, 17 Dec 2008)
Log Message:
-----------
added some threshold crossing helper funcs to mlab
Modified Paths:
--------------
trunk/matplotlib/lib/matplotlib/mlab.py
Modified: trunk/matplotlib/lib/matplotlib/mlab.py
===================================================================
--- trunk/matplotlib/lib/matplotlib/mlab.py 2008-12-17 14:55:42 UTC (rev
6647)
+++ trunk/matplotlib/lib/matplotlib/mlab.py 2008-12-17 14:57:28 UTC (rev
6648)
@@ -54,6 +54,16 @@
yourself stranded without scipy (and the far superior
scipy.integrate tools)
+:meth:`contiguous_regions`
+ return the indices of the regions spanned by some logical mask
+
+:meth:`cross_from_below`
+ return the indices where a 1D array crosses a threshold from below
+
+:meth:`cross_from_above`
+ return the indices where a 1D array crosses a threshold from above
+
+
record array helper functions
-------------------------------
@@ -3236,6 +3246,63 @@
boundaries.append((in_region, i+1))
return boundaries
+
+def cross_from_below(x, threshold):
+ """
+ return the indices into *x* where *x* crosses some threshold from
+ below, eg the i's where::
+
+ x[i-1]<threshold and x[i]>=threshold
+
+ Example code::
+
+ import matplotlib.pyplot as plt
+
+ t = np.arange(0.0, 2.0, 0.1)
+ s = np.sin(2*np.pi*t)
+
+ fig = plt.figure()
+ ax = fig.add_subplot(111)
+ ax.plot(t, s, '-o')
+ ax.axhline(0.5)
+ ax.axhline(-0.5)
+
+ ind = cross_from_below(s, 0.5)
+ ax.vlines(t[ind], -1, 1)
+
+ ind = cross_from_above(s, -0.5)
+ ax.vlines(t[ind], -1, 1)
+
+ plt.show()
+
+ .. seealso::
+
+ :func:`cross_from_above` and :func:`contiguous_regions`
+
+ """
+ x = np.asarray(x)
+ threshold = threshold
+ ind = np.nonzero( (x[:-1]<threshold) & (x[1:]>=threshold))[0]
+ if len(ind): return ind+1
+ else: return ind
+
+def cross_from_above(x, threshold):
+ """
+ return the indices into *x* where *x* crosses some threshold from
+ below, eg the i's where::
+
+ x[i-1]>threshold and x[i]<=threshold
+
+ .. seealso::
+
+ :func:`cross_from_below` and :func:`contiguous_regions`
+
+ """
+ x = np.asarray(x)
+ ind = np.nonzero( (x[:-1]>=threshold) & (x[1:]<threshold))[0]
+ if len(ind): return ind+1
+ else: return ind
+
##################################################
# Vector and path length geometry calculations
##################################################
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