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fnval for tensor splines

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Michael Brown
Michael Brown on 22 Apr 2012
Answered: Unai San Miguel on 15 Mar 2017
I want to evaluate a tensor spline at a set of vector x(i),y(i) couples to get the vector z(i). The command fnval(pp,{x, y}) returns a matrix of all combinations of x and y. Is there a syntax to get the vector z(i) other than the not so elegant diag(fnval(pp,{x, y}) ) ?

Answers (1)

Unai San Miguel
Unai San Miguel on 15 Mar 2017
fnval(pp, [x(:)'; y(:)'])?
From the fnval doc page
(...)
For an m-variate f with m>1, with f [d1,...,dr]-valued, x may be either an array, or else a cell array {x1,...,xm}.
  1. If x is an array, of size [n1,...,ns] say, then n1 must equal m, and v has size [d1,...,dr, n2,...,ns], with v(:,...,:, j2,...,js) the value of f at x(:,j2,...,js), – except that(1) d1, ..., dr is ignored in case f is scalar-valued, i.e., both r and n1 are 1;
(...)
In your case m = 2, d1 = 1, r = 1, [x(:)'; y(:)'] would be an array of size (2, length(x))

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