Error with own distance function when calculating Davies Bouldin

[bamaly]

I wanted to use my own distance function, as below:

distfun = @(XI,XJ)(1-abs(MyCorr(XI',XJ')));

MyCorr function:
function c = MyCorr(in1,in2)

% Average reference both sets of input maps
nO = size(in1,1);
Centering = eye(nO) - 1/nO;

in1 = Centering * in1;

if nargin < 2
    in2 = in1;
else
    in2 = Centering * in2;
end

% Compute covariance matrix between sets of input maps
covar = in1' * in2;
var1 = diag(in1' * in1);
var2 = diag(in2' * in2);

c = covar./sqrt(var1*var2');

While it works with the silhouette coefficient function, I get following error with Davies Bouldin:

Error using internal.stats.parseArgs
Invalid parameter name: Distance.

Error in clustering.evaluation.DaviesBouldinEvaluation (line 53)
      internal.stats.parseArgs(basePnames, baseDflts, varargin{:});

Error in evalclusters (line 190)
           obj = clustering.evaluation.DaviesBouldinEvaluation(X,YorFun,varargin{:});

Does someone no the whats the issue?
Thanks a lot in advance!

[adanjoga]

Hello Bamaly,
Sorry for my very late response.

Please have a look at the following list of CVI in CVIK:
https://github.com/adanjoga/cvik-toolbox/blob/master/CVIK-Supplementary%20material.pdf

In this case, the Davies-Boulding index won't work because it needs to compute the distance between centroids. In Table 1, column X indicates that the CVI requires the original data (X), whereas D indicates that the CVI can be applied over a distance matrix (as in your case). Thus, from Table 1, you can use all the CVIs with a mark in the "D" column, including the Silhouette index.

I hope this helps,