source: trunk/src/tps_eval.m @ 356

Last change on this file since 356 was 356, checked in by sommeria, 9 years ago

civ updated with new functions for opening files, consistently with uvmat
Bugs to be expected (use previous version then)

File size: 1.4 KB
Line 
1%'tps_eval': calculate the thin plate spline (tps) interpolation at a set of points
2% see tps_ceff for more information
3%------------------------------------------------------------------------
4% function EM = tps_eval(dsites,ctrs)
5%------------------------------------------------------------------------
6% OUPUT:
7% EM:  Mx(N+s) matrix representing the contributions at the M sites
8%   from unit sources located at each of the N centers, + (s+1) columns
9%   representing the contribution of the linear gradient part.
10%
11%INPUT:
12%dsites:  Nxs matrix representing the postions of the N 'observation' sites, with s the space dimension
13%ctrs: Mxs matrix  representing the postions of the M centers, sources of the tps,
14%
15% related functions:
16% tps_coeff, tps_eval_dxy
17
18function EM = tps_eval(dsites,ctrs)
19[M,s] = size(dsites); [N,s] = size(ctrs);
20EM = zeros(M,N);
21
22% calculate distance matrix: accumulate sum of squares of coordinate differences
23% The ndgrid command produces two MxN matrices:
24%   Dsite, consisting of N identical columns (each containing
25%       the d-th coordinate of the M data sites)
26%   Ctrs, consisting of M identical rows (each containing
27%       the d-th coordinate of the N centers)
28for d=1:s
29 [Dsites,Ctrs] = ndgrid(dsites(:,d),ctrs(:,d));
30 EM = EM + (Dsites-Ctrs).^2;%EM=square of distance matrices
31end
32
33% calculate tps
34np=find(EM~=0);
35EM(np) = EM(np).*log(EM(np))/2;%= tps formula r^2 log(r) (EM=r^2)
36
37% add linear gradient part:
38EM = [EM ones(M,1) dsites];
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