Provided by: libmath-gsl-perl_0.39-1build2_amd64 
NAME
Math::GSL::Histogram - Create and manipulate histograms of data
SYNOPSIS
use Math::GSL::Histogram qw/:all/;
my $H = gsl_histogram_alloc(100);
gsl_histogram_set_ranges_uniform($H,0,101);
gsl_histogram_increment($H, -50 ); # ignored
gsl_histogram_increment($H, 70 );
gsl_histogram_increment($H, 85.2 );
my $G = gsl_histogram_clone($H);
my $value = gsl_histogram_get($G, 70);
my ($max,$min) = (gsl_histogram_min_val($H), gsl_histogram_max_val($H) );
my $sum = gsl_histogram_sum($H);
DESCRIPTION
Here is a list of all the functions included in this module :
"gsl_histogram_alloc($n)" - This function allocates memory for a histogram with $n bins,
and returns a pointer to a newly created gsl_histogram struct. The bins and ranges are not
initialized, and should be prepared using one of the range-setting functions below in
order to make the histogram ready for use.
"gsl_histogram_calloc "
"gsl_histogram_calloc_uniform "
"gsl_histogram_free($h)" - This function frees the histogram $h and all of the memory
associated with it.
"gsl_histogram_increment($h, $x)" - This function updates the histogram $h by adding one
(1.0) to the bin whose range contains the coordinate $x. If $x lies in the valid range of
the histogram then the function returns zero to indicate success. If $x is less than the
lower limit of the histogram then the function returns $GSL_EDOM, and none of bins are
modified. Similarly, if the value of $x is greater than or equal to the upper limit of the
histogram then the function returns $GSL_EDOM, and none of the bins are modified. The
error handler is not called, however, since it is often necessary to compute histograms
for a small range of a larger dataset, ignoring the values outside the range of interest.
"gsl_histogram_accumulate($h, $x, $weight)" - This function is similar to
gsl_histogram_increment but increases the value of the appropriate bin in the histogram $h
by the floating-point number weight.
"gsl_histogram_find($h, $x)" - This function finds the bin number which covers the
coordinate $x in the histogram $h. The bin is located using a binary search. The search
includes an optimization for histograms with uniform range, and will return the correct
bin immediately in this case. If $x is found in the range of the histogram then the
function returns the bin number and returns $GSL_SUCCESS. If $x lies outside the valid
range of the histogram then the function returns $GSL_EDOM and the error handler is
invoked.
"gsl_histogram_get($h, $i)" - This function returns the contents of the $i-th bin of the
histogram $h. If $i lies outside the valid range of indices for the histogram then the
error handler is called with an error code of GSL_EDOM and the function returns 0.
"gsl_histogram_get_range($h, $i)" - This function finds the upper and lower range limits
of the $i-th bin of the histogram $h. If the index $i is valid then the corresponding
range limits are returned after the 0 in this order : lower and then upper. The lower
limit is inclusive (i.e. events with this coordinate are included in the bin) and the
upper limit is exclusive (i.e. events with the coordinate of the upper limit are excluded
and fall in the neighboring higher bin, if it exists). The function returns 0 to indicate
success. If i lies outside the valid range of indices for the histogram then the error
handler is called and the function returns an error code of $GSL_EDOM.
"gsl_histogram_max($h)" - This function returns the maximum upper limit of the histogram
$h. It provides a way of determining this value without accessing the gsl_histogram struct
directly.
"gsl_histogram_min($h)" - This function returns the minimum lower range limit of the
histogram $h. It provides a way of determining this value without accessing the
gsl_histogram struct directly.
"gsl_histogram_bins($h)" - This function returns the number of bins of the histogram $h
limit. It provides a way of determining this value without accessing the gsl_histogram
struct directly.
"gsl_histogram_reset($h)" - This function resets all the bins in the histogram $h to zero.
"gsl_histogram_calloc_range"
"gsl_histogram_set_ranges($h, $range, $size)" - This function sets the ranges of the
existing histogram $h using the array $range of size $size. The values of the histogram
bins are reset to zero. The $range array should contain the desired bin limits. The ranges
can be arbitrary, subject to the restriction that they are monotonically increasing. Note
that the size of the $range array should be defined to be one element bigger than the
number of bins. The additional element is required for the upper value of the final bin.
"gsl_histogram_set_ranges_uniform($h, $xmin, $xmax)" - This function sets the ranges of
the existing histogram $h to cover the range $xmin to $xmax uniformly. The values of the
histogram bins are reset to zero. The bin ranges are shown in the table below,
bin[0] corresponds to xmin <= x < xmin + d
bin[1] corresponds to xmin + d <= x < xmin + 2 d
......
bin[n-1] corresponds to xmin + (n-1)d <= x < xmax
where d is the bin spacing, d = (xmax-xmin)/n.
"gsl_histogram_memcpy($dest, $src)" - This function copies the histogram $src into the
pre-existing histogram $dest, making $dest into an exact copy of $src. The two histograms
must be of the same size.
"gsl_histogram_clone($src)" - This function returns a pointer to a newly created histogram
which is an exact copy of the histogram $src.
"gsl_histogram_max_val($h)" - This function returns the maximum value contained in the
histogram bins.
"gsl_histogram_max_bin($h)" - This function returns the index of the bin containing the
maximum value. In the case where several bins contain the same maximum value the smallest
index is returned.
"gsl_histogram_min_val($h)" - This function returns the minimum value contained in the
histogram bins.
"gsl_histogram_min_bin($h)" - This function returns the index of the bin containing the
minimum value. In the case where several bins contain the same maximum value the smallest
index is returned.
"gsl_histogram_equal_bins_p($h1, $h2)" - This function returns 1 if the all of the
individual bin ranges of the two histograms are identical, and 0 otherwise.
"gsl_histogram_add($h1, $h2)" - This function adds the contents of the bins in histogram
$h2 to the corresponding bins of histogram $h1, i.e. h'_1(i) = h_1(i) + h_2(i). The two
histograms must have identical bin ranges.
"gsl_histogram_sub($h1, $h2)" - This function subtracts the contents of the bins in
histogram $h2 from the corresponding bins of histogram $h1, i.e. h'_1(i) = h_1(i) -
h_2(i). The two histograms must have identical bin ranges.
"gsl_histogram_mul($h1, $h2)" - This function multiplies the contents of the bins of
histogram $h1 by the contents of the corresponding bins in histogram $h2, i.e. h'_1(i) =
h_1(i) * h_2(i). The two histograms must have identical bin ranges.
"gsl_histogram_div($h1, $h2)" - This function divides the contents of the bins of
histogram $h1 by the contents of the corresponding bins in histogram $h2, i.e. h'_1(i) =
h_1(i) / h_2(i). The two histograms must have identical bin ranges.
"gsl_histogram_scale($h, $scale)" - This function multiplies the contents of the bins of
histogram $h by the constant $scale, i.e. h'_1(i) = h_1(i) * scale.
"gsl_histogram_shift($h, $offset)" - This function shifts the contents of the bins of
histogram $h by the constant $offset, i.e. h'_1(i) = h_1(i) + offset.
"gsl_histogram_sigma($h)" - This function returns the standard deviation of the
histogrammed variable, where the histogram is regarded as a probability distribution.
Negative bin values are ignored for the purposes of this calculation. The accuracy of the
result is limited by the bin width.
"gsl_histogram_mean($h)" - This function returns the mean of the histogrammed variable,
where the histogram is regarded as a probability distribution. Negative bin values are
ignored for the purposes of this calculation. The accuracy of the result is limited by the
bin width.
"gsl_histogram_sum($h)" - This function returns the sum of all bin values. Negative bin
values are included in the sum.
"gsl_histogram_fwrite($stream, $h)" - This function writes the ranges and bins of the
histogram $h to the stream $stream, which has been opened by the gsl_fopen function from
the Math::GSL module, in binary format. The return value is 0 for success and $GSL_EFAILED
if there was a problem writing to the file. Since the data is written in the native binary
format it may not be portable between different architectures.
"gsl_histogram_fread($stream, $h)" - This function reads into the histogram $h from the
open stream $stream, which has been opened by the gsl_fopen function from the Math::GSL
module, in binary format. The histogram $h must be preallocated with the correct size
since the function uses the number of bins in $h to determine how many bytes to read. The
return value is 0 for success and $GSL_EFAILED if there was a problem reading from the
file. The data is assumed to have been written in the native binary format on the same
architecture.
"gsl_histogram_fprintf($stream, $h, $range_format, $bin_format)" - This function writes
the ranges and bins of the histogram $h line-by-line to the stream $stream (from the
gsl_fopen function from the Math::GSL module) using the format specifiers $range_format
and $bin_format. These should be one of the %g, %e or %f formats for floating point
numbers. The function returns 0 for success and $GSL_EFAILED if there was a problem
writing to the file. The histogram output is formatted in three columns, and the columns
are separated by spaces, like this,
range[0] range[1] bin[0]
range[1] range[2] bin[1]
range[2] range[3] bin[2]
....
range[n-1] range[n] bin[n-1]
The values of the ranges are formatted using range_format and the value of the bins
are formatted using bin_format. Each line contains the lower and upper limit of the
range of the bins and the value of the bin itself. Since the upper limit of one bin is
the lower limit of the next there is duplication of these values between lines but
this allows the histogram to be manipulated with line-oriented tools.
"gsl_histogram_fscanf($stream, $h)" - This function reads formatted data from the stream
$stream, which has been opened by the gsl_fopen function from the Math::GSL module, into
the histogram $h. The data is assumed to be in the three-column format used by
gsl_histogram_fprintf. The histogram $h must be preallocated with the correct length since
the function uses the size of $h to determine how many numbers to read. The function
returns 0 for success and $GSL_EFAILED if there was a problem reading from the file.
"gsl_histogram_pdf_alloc($n)" - This function allocates memory for a probability
distribution with $n bins and returns a pointer to a newly initialized gsl_histogram_pdf
struct. If insufficient memory is available a null pointer is returned and the error
handler is invoked with an error code of $GSL_ENOMEM.
"gsl_histogram_pdf_init($p, $h)" - This function initializes the probability distribution
$p with the contents of the histogram $h. If any of the bins of $h are negative then the
error handler is invoked with an error code of $GSL_EDOM because a probability
distribution cannot contain negative values.
"gsl_histogram_pdf_free($p)" - This function frees the probability distribution function
$p and all of the memory associated with it.
"gsl_histogram_pdf_sample($p, $r)" - This function uses $r, a uniform random number
between zero and one, to compute a single random sample from the probability distribution
$p. The algorithm used to compute the sample s is given by the following formula, s =
range[i] + delta * (range[i+1] - range[i]) where i is the index which satisfies sum[i] <=
r < sum[i+1] and delta is (r - sum[i])/(sum[i+1] - sum[i]).
EXAMPLES
The following example shows how to create a histogram with logarithmic bins with ranges [1,10), [10,100) and [100,1000).
$h = gsl_histogram_alloc (3);
# bin[0] covers the range 1 <= x < 10
# bin[1] covers the range 10 <= x < 100
# bin[2] covers the range 100 <= x < 1000
$range = [ 1.0, 10.0, 100.0, 1000.0 ];
gsl_histogram_set_ranges($h, $range, 4);
AUTHORS
Jonathan "Duke" Leto <jonathan@leto.net> and Thierry Moisan <thierry.moisan@gmail.com>
COPYRIGHT AND LICENSE
Copyright (C) 2008-2011 Jonathan "Duke" Leto and Thierry Moisan
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.