c_thresh.c

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#include <math.h>

#include <grass/gis.h>
#include <grass/raster.h>

void c_thresh(DCELL * result, DCELL * values, int n, const void *closure)
{
    DCELL thresh, threshx;
    double tval = *(const double *)closure;
    double epsilon = GRASS_EPSILON;
    int i;

    Rast_set_d_null_value(&thresh, 1);
    Rast_set_d_null_value(&threshx, 1);

    for (i = 0; i < n; i++) {
        /* already found */
        if (! Rast_is_d_null_value(&threshx))
            continue;

        if (Rast_is_d_null_value(&values[i]))
            continue;

        G_debug(2, "values[%d] %f, tval %f", i, values[i], tval);
        /* for GDD */
        epsilon = 10.;
        if (fabs(tval - values[i]) < epsilon ) {
            thresh = values[i];
            threshx = i + 1;
            G_debug(2, "values[%d] %f, thresh %f, threshx %f, diff %f", i, values[i], thresh, threshx, tval - values[i]);
        }
    }

    if (Rast_is_d_null_value(&threshx))
        Rast_set_d_null_value(result, 1);
    else
        *result = threshx;
}