c_sig.c

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/*!
   \file cluster/c_sig.c
 
   \brief Cluster library - Signatures
 
   (C) 2001-2009 by the GRASS Development Team
 
   This program is free software under the GNU General Public License
   (>=v2). Read the file COPYING that comes with GRASS for details.
 
   \author Original author CERL
 */
 
#include <grass/cluster.h>
 
/*!
   \brief Create signatures
 
   \param C pointer to Cluster structure
 
   \return 0
 */
int I_cluster_signatures(struct Cluster *C)
{
    int c, p, band1, band2;
    int n;
    double m1, m2;
    double p1, p2;
    double dn;
 
    /*
       fprintf (stderr, "c_sig: 1\n");
       fprintf (stderr, "  nclasses %d\n", C->nclasses);
       fprintf (stderr, "  npoints  %d\n", C->npoints );
       fprintf (stderr, "  nbands   %d\n", C->nbands  );
     */
    for (n = 0; n < C->nclasses; n++) {
        I_new_signature(&C->S);
    }
 
    for (p = 0; p < C->npoints; p++) {
        c = C->class[p];
        if (c < 0)
            continue;
        /*
           if (c >= C->nclasses)
           fprintf (stderr, " class[%d]=%d ** illegal **\n", p, c);
         */
        dn = n = C->count[c];
        if (n < 2)
            continue;
        for (band1 = 0; band1 < C->nbands; band1++) {
            m1 = C->sum[band1][c] / dn;
            p1 = C->points[band1][p];
            for (band2 = 0; band2 <= band1; band2++) {
                m2 = C->sum[band2][c] / dn;
                p2 = C->points[band2][p];
                C->S.sig[c].var[band1][band2] += (p1 - m1) * (p2 - m2);
            }
        }
    }
 
    for (c = 0; c < C->nclasses; c++) {
        dn = n = C->S.sig[c].npoints = C->count[c];
        if (n == 0)
            dn = 1.0;
        for (band1 = 0; band1 < C->nbands; band1++)
            C->S.sig[c].mean[band1] = C->sum[band1][c] / dn;
        dn = n = C->count[c] - 1;
        if (n < 1)
            continue;
        for (band1 = 0; band1 < C->nbands; band1++)
            for (band2 = 0; band2 <= band1; band2++)
                C->S.sig[c].var[band1][band2] /= dn;
        C->S.sig[c].status = 1;
    }
 
    return 0;
}