kdata_pmfvar —
compute probability mass function variance of
data
#include <cairo.h>
#include <kplot.h>
double
kdata_pmfmean(const struct kdata
*data);
The kdata_pmfmean function compute the
variance of its data as if it were a probability mass function.
If the data source has zero entries or the sum of the y values is
0.0, kdata_pmfmean returns 0.0. Otherwise, it
returns the variance.