Armin Moser wrote: > Jeff Whitaker wrote: > >> Armin Moser wrote: >> >>> Hi, >>> >>> I would like to interpolate an array of shape (801,676) to regularily >>> spaced datapoints using griddata. This interpolation is quick if the >>> (x,y) supporting points are computed as X,Y = meshgrid(x,y). If this >>> condition is not fullfilled the delaunay triangulation is extremely >>> slow, i.e. not useable. Is this a known property of the used >>> triangulation? The triangulation can be performed with matlab without >>> any problems. >>> >>> Armin >>> >>> >> Armin: You could try installing the natgrid toolkit and see if that >> speeds up griddata at all. If not, please post a test script with data >> and maybe we can figure out what is going on. >> > I have already tried natgrid and it didn't improve the situation. As > suggested I append a script demonstrating the problem. > > Thanks > Armin >
Armin: On my mac, your two benchmarks take 15 and 14 seconds. Do you consider that too slow? Perhaps this is just a toy example to test griddata, but I assume you realize that you wouldn't normally use griddata to interpolate data on one regular grid to another regular grid. griddata is strictly for interpolating scatter data (not on a regular mesh) to a regular mesh. -Jeff > ------8<------------- > from numpy import * > from pylab import * > import time > > deg2rad = pi/180.0 > ai = 0.12*deg2rad > x = linspace(13,40,676) > y = linspace(10,22,801) > > x = x*deg2rad > y = y*deg2rad > [x,y] = meshgrid(x,y) > z = (x**2+y**2) > > xi = linspace(x.min(),x.max(),x.shape[1]) > yi = linspace(y.min(),y.max(),y.shape[0]) > tic= time.time() > zi = griddata(x.flatten(),y.flatten(),z.flatten(),xi,yi) > toc = time.time() > print toc-tic > > fac = 2*pi/1.2681 > nx = fac * (cos(y)*cos(x) - cos(ai)) > ny = fac * (cos(y)*sin(x)) > nz = fac * (sin(y) + sin(ai)) > np = sqrt(nx**2 + ny**2) > > z = (np**2+nz**2)*exp(-0.001*nz) > > xi = linspace(np.min(),np.max(),x.shape[1]) > yi = linspace(nz.min(),nz.max(),y.shape[0]) > tic = time.time() > zi = griddata(np.flatten(),nz.flatten(),z.flatten(),xi,yi) > toc = time.time() > print toc-tic > -- Jeffrey S. Whitaker Phone : (303)497-6313 Meteorologist FAX : (303)497-6449 NOAA/OAR/PSD R/PSD1 Email : jeffrey.s.whita...@noaa.gov 325 Broadway Office : Skaggs Research Cntr 1D-113 Boulder, CO, USA 80303-3328 Web : http://tinyurl.com/5telg ------------------------------------------------------------------------------ Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA -OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise -Strategies to boost innovation and cut costs with open source participation -Receive a $600 discount off the registration fee with the source code: SFAD http://p.sf.net/sfu/XcvMzF8H _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
