gsl_histogram2d extensions

[Achim Gaedke <Achim dot Gaedke at uni-koeln dot de>]

Here are the cvs-diffs for the new histogram2d functions:

double
gsl_histogram2d_psum(const gsl_histogram2d *h, size_t i_begin, size_t i_end,
                    size_t j_begin, size_t j_end);

double
gsl_histogram2d_xmean (const gsl_histogram2d * h);

double
gsl_histogram2d_ymean (const gsl_histogram2d * h);

double
gsl_histogram2d_xsigma (const gsl_histogram2d * h);

double
gsl_histogram2d_ysigma (const gsl_histogram2d * h);

double
gsl_histogram2d_cov (const gsl_histogram2d * h);

For gsl_histogram2d_psum the discussion was open, so I did not know what to do
with it.
The function gsl_histogram2d_sum was defined in histogram/maxval2d.c, but should
move to histogram/stat2d.c. That file is new and attached, too.

There is additional test code for histogram/test2d.c and some supplements for
doc/histogram.texi .

Have a lot of fun with it!

Achim

PS: Hope, attachments make no trouble with the list.

Attachment: diff.histogram2d
Description: Binary data

Attachment: stat2d.c
Description: Binary data