griddedInterpolant error "Interpolation requires at least two sample points for each grid dimension."

139 views (last 30 days)
I'm systematically getting this error trying to use griddedInterpolant. Here's a simple example:
bp1 = [0:1:10];
bp2 = [5:0.5:10];
bp3 = [2:0.1:3];
tv = bp1.*bp3+bp2.^2
f=griddedInterpolant(bp1,bp2,bp3,tv)
But I get the error:
Error using griddedInterpolant
Interpolation requires at least two sample points for each grid dimension.
What have I missed?

Answers (2)

Voss
Voss on 1 Dec 2023
The points (bp1, bp2, bp3) in 3d space do not form a grid. They are equally-spaced points along a line segment from (0,5,2) to (10,10,3).
You can use ndgrid to construct a set of points that form a grid from your bp1, bp2, bp3 vectors.
bp1 = 0:1:10;
bp2 = 5:0.5:10;
bp3 = 2:0.1:3;
% tv = bp1.*bp3+bp2.^2;
[BP1,BP2,BP3] = ndgrid(bp1,bp2,bp3);
TV = BP1.*BP3+BP2.^2;
f=griddedInterpolant(BP1,BP2,BP3,TV)
f =
griddedInterpolant with properties: GridVectors: {[0 1 2 3 4 5 6 7 8 9 10] [5 5.5000 6 6.5000 7 7.5000 8 8.5000 9 9.5000 10] [2 2.1000 2.2000 2.3000 2.4000 2.5000 2.6000 2.7000 2.8000 2.9000 3]} Values: [11×11×11 double] Method: 'linear' ExtrapolationMethod: 'linear'
  5 Comments
Stephen23
Stephen23 on 3 Dec 2023
Either call RESHAPE on each column of data.
Or simply call SCATTEREDINTERPOLANT and let it do the work for you.
Dave Hall
Dave Hall on 3 Dec 2023
Unfortunately, scatteredInterpolant is limited to 3 parameters. I'll try to reshape each parameter plus the result vector.

Sign in to comment.


Star Strider
Star Strider on 3 Dec 2023
The interpn function could be an option. You will need to experiment with the ndgrid function to determine how best to reshape the first 5 columns of your data to conform to it (if they indeed need reshaping — they may not) and then do the interpolation. I am not certain how easy it would be to make sense of the results, much less plot them, since everything in this universe is limited to 3 spatial dimensions and time, last I heard.
If you only want to interpolate specific points or ranges of points within the limits of the original vectors (so not extrapolating), interpn could do what you want.

Categories

Find more on Interpolation in Help Center and File Exchange

Products


Release

R2021a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!