Revision: 7287
http://matplotlib.svn.sourceforge.net/matplotlib/?rev=7287&view=rev
Author: jswhit
Date: 2009-07-23 12:10:18 +0000 (Thu, 23 Jul 2009)
Log Message:
-----------
add 'interp' keyword to griddata. Can be set to 'linear' to get faster
linear interpolation using Delaunay package. Default is 'nn' (natural
neighbor).
Modified Paths:
--------------
trunk/matplotlib/CHANGELOG
trunk/matplotlib/lib/matplotlib/mlab.py
Modified: trunk/matplotlib/CHANGELOG
===================================================================
--- trunk/matplotlib/CHANGELOG 2009-07-22 13:58:18 UTC (rev 7286)
+++ trunk/matplotlib/CHANGELOG 2009-07-23 12:10:18 UTC (rev 7287)
@@ -1,3 +1,7 @@
+2009-07-22 Added an 'interp' keyword to griddata so the faster linear
+ interpolation method can be chosen. Default is 'nn', so
+ default behavior (using natural neighbor method) is unchanged (JSW)
+
2009-07-22 Improved boilerplate.py so that it generates the correct
signatures for pyplot functions. - JKS
Modified: trunk/matplotlib/lib/matplotlib/mlab.py
===================================================================
--- trunk/matplotlib/lib/matplotlib/mlab.py 2009-07-22 13:58:18 UTC (rev
7286)
+++ trunk/matplotlib/lib/matplotlib/mlab.py 2009-07-23 12:10:18 UTC (rev
7287)
@@ -2621,7 +2621,7 @@
if opened:
fh.close()
-def griddata(x,y,z,xi,yi):
+def griddata(x,y,z,xi,yi,interp='nn'):
"""
``zi = griddata(x,y,z,xi,yi)`` fits a surface of the form *z* =
*f*(*x*, *y*) to the data in the (usually) nonuniformly spaced
@@ -2633,7 +2633,8 @@
A masked array is returned if any grid points are outside convex
hull defined by input data (no extrapolation is done).
- Uses natural neighbor interpolation based on Delaunay
+ If interp keyword is set to '`nn`' (default),
+ uses natural neighbor interpolation based on Delaunay
triangulation. By default, this algorithm is provided by the
:mod:`matplotlib.delaunay` package, written by Robert Kern. The
triangulation algorithm in this package is known to fail on some
@@ -2646,6 +2647,14 @@
algorithm, otherwise it will use the built-in
:mod:`matplotlib.delaunay` package.
+ If the interp keyword is set to '`linear`', then linear interpolation
+ is used instead of natural neighbor. In this case, the output grid
+ is assumed to be regular with a constant grid spacing in both the x and
+ y directions. For regular grids with nonconstant grid spacing, you
+ must use natural neighbor interpolation. Linear interpolation is only
valid if
+ :mod:`matplotlib.delaunay` package is used - :mod:`mpl_tookits.natgrid`
+ only provides natural neighbor interpolation.
+
The natgrid matplotlib toolkit can be downloaded from
http://sourceforge.net/project/showfiles.php?group_id=80706&package_id=142792
"""
@@ -2674,6 +2683,9 @@
y = y.compress(z.mask == False)
z = z.compressed()
if _use_natgrid: # use natgrid toolkit if available.
+ if interp != 'nn':
+ raise ValueError("only natural neighor interpolation"
+ " allowed when using natgrid toolkit in griddata.")
if xi.ndim == 2:
xi = xi[0,:]
yi = yi[:,0]
@@ -2701,8 +2713,17 @@
# triangulate data
tri = delaunay.Triangulation(x,y)
# interpolate data
- interp = tri.nn_interpolator(z)
- zo = interp(xi,yi)
+ if interp == 'nn':
+ interp = tri.nn_interpolator(z)
+ zo = interp(xi,yi)
+ elif interp == 'linear':
+ interp = tri.linear_interpolator(z)
+ zo = interp[yi.min():yi.max():complex(0,yi.shape[0]),
+ xi.min():xi.max():complex(0,xi.shape[1])]
+ else:
+ raise ValueError("interp keyword must be one of"
+ " 'linear' (for linear interpolation) or 'nn'"
+ " (for natural neighbor interpolation). Default is 'nn'.")
# mask points on grid outside convex hull of input data.
if np.any(np.isnan(zo)):
zo = np.ma.masked_where(np.isnan(zo),zo)
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