scaleEpsilonAccordingToRbfType

preProcessIfNeeded Some RBF types require working on scaled
    data and/or scaled parameters, this is the function where
    these special cases are handled

0001 function epsilon = scaleEpsilonAccordingToRbfType(rbfType, epsilon, x, y, z)
0002 %preProcessIfNeeded Some RBF types require working on scaled
0003 %    data and/or scaled parameters, this is the function where
0004 %    these special cases are handled
0005 
0006 if strcmpi(rbfType, 'greenwithtension') || strcmpi(rbfType, 'greenregularizedwithtension')
0007     % greenWithTensionRBF expects the epsilon (tension parameter) to be between 0..1
0008     if epsilon < 0 || epsilon >= 1
0009         error('greenWithTensionRBF expects the tension parameter (epsilon) to be 0 <= epsilon < 1!');
0010     end
0011     
0012     % Length scale
0013     % DevNote: This parameter (\alpha in the original reference) is an
0014     % heuristic, and in GMT is computed from the range of values in of the
0015     % QUERY points, so if you are using this formula with the data points
0016     % that is a different approximation!
0017     IM = sqrt (-1);
0018     lengthScale = 50/abs(max(x(:)) - min(x(:)) + IM * (max(y(:)) - min(y(:))));
0019     
0020     % With the following transformation, epsilon changes to be the
0021     % parameter 'p' in the original reference (Wessel and Bercovici, 1998)
0022     epsilon = sqrt(epsilon/(1-epsilon));
0023     epsilon = epsilon*lengthScale;
0024 end
0025 
0026 end