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- /* histogram/pdf2d.c
- *
- * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Brian Gough
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 3 of the License, or (at
- * your option) any later version.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
- */
- #include "gsl__config.h"
- #include <stdlib.h>
- #include "gsl_errno.h"
- #include "gsl_histogram.h"
- #include "gsl_histogram2d.h"
- #include "gsl_histogram__find.c"
- int
- gsl_histogram2d_pdf_sample (const gsl_histogram2d_pdf * p,
- double r1, double r2,
- double *x, double *y)
- {
- size_t k;
- int status;
- /* Wrap the exclusive top of the bin down to the inclusive bottom of
- the bin. Since this is a single point it should not affect the
- distribution. */
- if (r2 == 1.0)
- {
- r2 = 0.0;
- }
- if (r1 == 1.0)
- {
- r1 = 0.0;
- }
- status = find (p->nx * p->ny, p->sum, r1, &k);
- if (status)
- {
- GSL_ERROR ("cannot find r1 in cumulative pdf", GSL_EDOM);
- }
- else
- {
- size_t i = k / p->ny;
- size_t j = k - (i * p->ny);
- double delta = (r1 - p->sum[k]) / (p->sum[k + 1] - p->sum[k]);
- *x = p->xrange[i] + delta * (p->xrange[i + 1] - p->xrange[i]);
- *y = p->yrange[j] + r2 * (p->yrange[j + 1] - p->yrange[j]);
- return GSL_SUCCESS;
- }
- }
- gsl_histogram2d_pdf *
- gsl_histogram2d_pdf_alloc (const size_t nx, const size_t ny)
- {
- const size_t n = nx * ny;
- gsl_histogram2d_pdf *p;
- if (n == 0)
- {
- GSL_ERROR_VAL ("histogram2d pdf length n must be positive integer",
- GSL_EDOM, 0);
- }
- p = (gsl_histogram2d_pdf *) malloc (sizeof (gsl_histogram2d_pdf));
- if (p == 0)
- {
- GSL_ERROR_VAL ("failed to allocate space for histogram2d pdf struct",
- GSL_ENOMEM, 0);
- }
- p->xrange = (double *) malloc ((nx + 1) * sizeof (double));
- if (p->xrange == 0)
- {
- free (p); /* exception in constructor, avoid memory leak */
- GSL_ERROR_VAL ("failed to allocate space for histogram2d pdf xranges",
- GSL_ENOMEM, 0);
- }
- p->yrange = (double *) malloc ((ny + 1) * sizeof (double));
- if (p->yrange == 0)
- {
- free (p->xrange);
- free (p); /* exception in constructor, avoid memory leak */
- GSL_ERROR_VAL ("failed to allocate space for histogram2d pdf yranges",
- GSL_ENOMEM, 0);
- }
- p->sum = (double *) malloc ((n + 1) * sizeof (double));
- if (p->sum == 0)
- {
- free (p->yrange);
- free (p->xrange);
- free (p); /* exception in constructor, avoid memory leak */
- GSL_ERROR_VAL ("failed to allocate space for histogram2d pdf sums",
- GSL_ENOMEM, 0);
- }
- p->nx = nx;
- p->ny = ny;
- return p;
- }
- int
- gsl_histogram2d_pdf_init (gsl_histogram2d_pdf * p, const gsl_histogram2d * h)
- {
- size_t i;
- const size_t nx = p->nx;
- const size_t ny = p->ny;
- const size_t n = nx * ny;
- if (nx != h->nx || ny != h->ny)
- {
- GSL_ERROR ("histogram2d size must match pdf size", GSL_EDOM);
- }
- for (i = 0; i < n; i++)
- {
- if (h->bin[i] < 0)
- {
- GSL_ERROR ("histogram bins must be non-negative to compute"
- "a probability distribution", GSL_EDOM);
- }
- }
- for (i = 0; i < nx + 1; i++)
- {
- p->xrange[i] = h->xrange[i];
- }
- for (i = 0; i < ny + 1; i++)
- {
- p->yrange[i] = h->yrange[i];
- }
- {
- double mean = 0, sum = 0;
- for (i = 0; i < n; i++)
- {
- mean += (h->bin[i] - mean) / ((double) (i + 1));
- }
- p->sum[0] = 0;
- for (i = 0; i < n; i++)
- {
- sum += (h->bin[i] / mean) / n;
- p->sum[i + 1] = sum;
- }
- }
- return GSL_SUCCESS;
- }
- void
- gsl_histogram2d_pdf_free (gsl_histogram2d_pdf * p)
- {
- free (p->xrange);
- free (p->yrange);
- free (p->sum);
- free (p);
- }
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