griddedInterpolant bug
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There is a bug with the griddedInterpolant function with nearest and linear methods. If the query set contains any out-of-range values, the entire evaluated set is NaN, not just the results corresponding to the out-of-range queries.
In contrast, the griddedInterpolant with cubic interpolation method returns NaN for only out-of-range queries and correctly evaluates the in-range queries.
This is an problem for me because I'd like to use the linear method. I'm currently filtering out the out-of-range values from the query before processing, but the best solution would be to get the linear griddedInterpolant to work as it should. How should I fix it?
This bug is demonstrated by the following example script:
[X,Y,Z] = ndgrid(1:10,1:10,1:10);
V = X.^.5 + Y.^.5 + Z.^.5;
nearestInterp = griddedInterpolant(X,Y,Z,V,'nearest');
linearInterp = griddedInterpolant(X,Y,Z,V,'linear');
cubicInterp = griddedInterpolant(X,Y,Z,V,'cubic');
splineInterp = griddedInterpolant(X,Y,Z,V,'spline');
[Xq,Yq,Zq] = ndgrid(0:.5:10,0:.5:10,0:.5:10);
Vq_nearest = nearestInterp(Xq,Yq,Zq);
Vq_linear = linearInterp(Xq,Yq,Zq);
Vq_cubic = cubicInterp(Xq,Yq,Zq);
Vq_spline = splineInterp(Xq,Yq,Zq);
Thanks, Nick
3 个评论
Honglei Chen
2012-3-26
Hi Nick, which version of MATLAB are you using, I tried this in R2012a and couldn't reproduce it.
Marc Lalancette
2012-10-18
I know this is an old thread but I also ran into this problem, using version 2011b. Is it possible to get this fixed without paying hundreds of dollars for a new version?
The best solution, other than upgrading, is probably to create your own wrapper that separates out-of-bounds values from inbound values and only calls griddedInterpolant on the latter. You would do that only when the linear interpolation method is active, of course.
采纳的回答
Sean de Wolski
2012-10-18
0 个投票
This behavior was fixed in R2012a. If you are current on SMS, you can download R2012a or R2012b for free.
5 个评论
Wen
2014-5-28
I'm seeing the same problem for spline in R2014a.
Sean de Wolski
2014-5-28
Wen, can you provide a minimal working example?
Wen
2014-6-1
Sorry, I realized the problem I found was a bit different then the topic question. It has to do with ignoring NaN values in V when making the interpolated surface. If nearest, linear, or cubic are used, I can get the values of the interpolated surface as long as it's not close to the x, y, z values at which V is NaN. However, the spline option makes everything NaN instead of only at those x, y, z values.
I added one line to the one Nick gave:
[X,Y,Z] = ndgrid(1:10,1:10,1:10);
V = X.^.5 + Y.^.5 + Z.^.5;
V(10, 10, 10) = NaN;
nearestInterp = griddedInterpolant(X,Y,Z,V,'nearest');
linearInterp = griddedInterpolant(X,Y,Z,V,'linear');
cubicInterp = griddedInterpolant(X,Y,Z,V,'cubic');
splineInterp = griddedInterpolant(X,Y,Z,V,'spline');
[Xq,Yq,Zq] = ndgrid(0:.5:10,0:.5:10,0:.5:10);
Vq_nearest = nearestInterp(Xq,Yq,Zq);
Vq_linear = linearInterp(Xq,Yq,Zq);
Vq_cubic = cubicInterp(Xq,Yq,Zq);
Vq_spline = splineInterp(Xq,Yq,Zq);
Wen
2014-6-2
Ah ok, makes sense. I see cubic has more NaNs in its interpolated values than linear, and it depends on 4 points (or is it 3?) rather than 2. Okay.
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