|SOM Toolbox||Online documentation||http://www.cis.hut.fi/projects/somtoolbox/|
P = sammon(D, P, varargin)
SAMMON Computes Sammon's mapping of a data set. P = sammon(D, P, [value], [mode], [alpha], [Mdist]) P = sammon(D,2); % projection to 2-dim space P = sammon(sMap,3); % projects the codebook vectors P = sammon(sMap,3,,,,Md) % uses distance matrix Md som_grid(sMap,'Coord',P) % visualization of map projection Input and output arguments ('s are optional): D (matrix) size dlen x dim, data to be projected (struct) data or map struct P (scalar) output dimension (matrix) size dlen x odim, initial projection matrix [value] (scalar) all different modes (the next argument) require a value, default = 100 [mode] (string) 'steps' or 'errlimit' or 'errchange' or 'seconds', see below, default is 'steps' [alpha] (scalar) iteration step size, default = 0.2 [Dist] (matrix) pairwise distance matrix, size dlen x dlen. If the distances in the input space should be calculated otherwise than as euclidian distances, the distance from each vector to each other vector can be given here, size dlen x dlen. For example PDIST function can be used to calculate the distances: Dist = squareform(pdist(D,'mahal')); P (matrix) size dlen x odim, the projections The output dimension must be 2 or higher but (naturally) lower than data set dimension. The mode argument determines the end condition for iteration. If the mode argument is used, also the value argument has to be specified. Different mode possibilities are: 'steps' the iteration is terminated when it is run
'errlimit' steps, the iteration is terminated when projection error is lower than , 'errchange' the iteration is terminated when change between projection error on two successive iteration rounds is less than percent of total error, and 'seconds' the iteration is terminated after seconds of iteration. See also CCA, PCAPROJ, SOM_GRID.