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21.14 2D Histogram allocation

The functions for allocating memory to a 2D histogram follow the style of malloc and free. In addition they also perform their own error checking. If there is insufficient memory available to allocate a histogram then the functions call the error handler (with an error number of GSL_ENOMEM) in addition to returning a null pointer. Thus if you use the library error handler to abort your program then it isn't necessary to check every 2D histogram alloc.

— Function: gsl_histogram2d * gsl_histogram2d_alloc (size_t nx, size_t ny)

This function allocates memory for a two-dimensional histogram with nx bins in the x direction and ny bins in the y direction. The function returns a pointer to a newly created gsl_histogram2d struct. If insufficient memory is available a null pointer is returned and the error handler is invoked with an error code of GSL_ENOMEM. The bins and ranges must be initialized with one of the functions below before the histogram is ready for use.

— Function: int gsl_histogram2d_set_ranges (gsl_histogram2d * h, const double xrange[], size_t xsize, const double yrange[], size_t ysize)

This function sets the ranges of the existing histogram h using the arrays xrange and yrange of size xsize and ysize respectively. The values of the histogram bins are reset to zero.

— Function: int gsl_histogram2d_set_ranges_uniform (gsl_histogram2d * h, double xmin, double xmax, double ymin, double ymax)

This function sets the ranges of the existing histogram h to cover the ranges xmin to xmax and ymin to ymax uniformly. The values of the histogram bins are reset to zero.

— Function: void gsl_histogram2d_free (gsl_histogram2d * h)

This function frees the 2D histogram h and all of the memory associated with it.