Re: 4D interpolation

[Ben Abbott]

On May 26, 2008, at 3:31 AM, thanatos187 wrote:

> Ben Abbott wrote:
> > On May 20, 2008, at 3:52 AM, thanatos187 wrote:
> >
> > > Hi
> > > I want to interpolate my values with the spline method. I did it
> > > with the
> > > command:
> > > vi = interpn(u,v,w,x,z,uu,vv,ww,xx,'spline');
> > > where u,v,w,x are vectors of the same length defining the point with
> > > the
> > > value z. uu,vv,ww,xx are creaed by the ndgrid command. i got the  
> > > error
> > > message: "wrong number or incorrectly formatted input argument".
> > >
> > > thanks for any help
> > > Thanatos
> >
> > Can you post a simple example? Does the problem occur for "nearest",
> > "linear", or "cubic" interpolation?
> >
> > Ben
> >
> > It occurs for all methods. I want to use a spline interpolation. I  
> > have
> > 1500 data points, so the length of the colum vectors are 1500.
> > uu,vv,ww,xx, are matrixes of the size (10  10  10  10)
> >
> > thanatos

I tried a 3D and 4D example.

clear all

v1 = 0:0.2:2;
v2 = v1;
v3 = v1;
[x1,x2,x3] = ndgrid(v1,v2,v3);
y = (x1.*x2 + x1.*x2.^2).*x3;
z = interpn(x1,x2,x3,y,v1,v2,v3,'linear')

v4 = v1;
[x1,x2,x3,x4] = ndgrid(v1,v2,v3,v4);
y = (x1.*x2 + x1.*x2.^2).*x3./(1+x4);
z = interpn(x1,x2,x3,x4,y,v1,v2,v3,v4,'linear')

Both of these work for me. Please verify they work for you as well.

Ben