Yes, you are absolutely correct. I did not realize that I did not actually
evaluate the function over a grid, makes sense that interpolation fails. I
thought that since I created the two axis vectors the function evaluation
occurs over the entire domain, meshgrid is what I was missing.
thanks,
Shahar
On Jan 9, 2013, at 8:45 PM, Ian Thomas wrote:
> On 9 January 2013 09:32, Shahar Shani-Kadmiel <kadm...@post.bgu.ac.il> wrote:
> Hi,
>
> I'm trying to contour some data that I have and the griddata line fails. I
> tried running it on some synthetically generated data and I get the same
> IndexError. Any Ideas?
>
> Here is the example with the synthetic data:
>
> x = y = arange(-10,10,0.01)
>
> z = x**2+y**3
>
> xi = yi = linspace(-10.1, 10.1, 100)
>
> zi = griddata(x, y, z, xi, yi)
> ---------------------------------------------------------------------------
> IndexError Traceback (most recent call last)
> <ipython-input-52-0458ab6ea672> in <module>()
> ----> 1 zi = griddata(x, y, z, xi, yi)
>
> /Library/Frameworks/Python.framework/Versions/7.3/lib/python2.7/site-packages/matplotlib/mlab.py
> in griddata(x, y, z, xi, yi, interp)
> 2766 xi,yi = np.meshgrid(xi,yi)
> 2767 # triangulate data
> -> 2768 tri = delaunay.Triangulation(x,y)
>
> Hello Shahar,
>
> I think that your simple example is probably not what you intended. Your
> (x,y) points are all defined on the straight line from (-10,-10) to (10,10).
> The Delaunay triangulation of these points (which is what griddata does) is
> not very interesting! Perhaps you wanted (x,y) defined on the 2D grid from
> (-10,-10) to (10,10), in which case you should follow the x = y ... line
> with, for example:
> x, y = meshgrid(x, y)
> (see numpy.meshgrid for further details).
>
> You may still obtain the same IndexError, and the traceback shows this is
> happening in the delaunay.Triangulation function call. The matplotlib
> delaunay package is not particularly robust, and can have problems handling
> regularly-spaced data points. The griddata documentation explains some of
> this, see http://matplotlib.org/api/mlab_api.html#matplotlib.mlab.griddata.
>
> To avoid the problem, the griddata documentation explains one possible way
> that uses the natgrid algorithm. A simpler solution that I often use is to
> add a very small amount of noise to my regularly-spaced (x,y) points using
> the numpy.random module. I can give more details if you wish.
>
> Ian
------------------------------------------------------------------------------
Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS,
MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current
with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft
MVPs and experts. ON SALE this month only -- learn more at:
http://p.sf.net/sfu/learnmore_122712
_______________________________________________
Matplotlib-users mailing list
Matplotlib-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/matplotlib-users
