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KDATA_STDDEV_ALLOC(3)	     Library Functions Manual	   KDATA_STDDEV_ALLOC(3)

NAME
     kdata_stddev_alloc -- allocate standard deviation data for plotting

LIBRARY
     libkplot

SYNOPSIS
     #include <cairo.h>
     #include <kplot.h>

     struct kdata *
     kdata_stddev_alloc(struct kdata *source);

DESCRIPTION
     The   kdata_stddev_alloc  creates	a  reference-counted  data  sources  for
     kplot(3).	It attaches to zero or more existing data sources and, when they
     update their values, tracks the standard deviation (via the unbiased sample
     variance) of sequence of updated values.

     It attaches to zero or more existing data sources	and,  when  they  update
     their  values  per-index,	tracks	the standard deviation (via the unbiased
     sample variance) of the sequence of updated values.  Thus,  if  a	standard
     deviation data source is attached to two sources, its y-value for pair zero
     will reflect the standard deviation from the mean of all values set to pair
     zero's  y-value in the sources.  Note that the indexing is absolute: if at-
     tached to a bucket or histogram, pair index zero refers to the first inter-
     nal data storage, not storage mapped from the bucket or histogram.

     If source is not NULL, the internal buffer is initialised to  the	size  of
     the  source and all of its x values.  The standard deviation is initialised
     to zero with zero updates.  Otherwise, the  internal  buffer  is  sized  to
     zero.

     Further data sources may be attached with kdata_stddev_attach(3).

RETURN VALUES
     kdata_stddev_alloc returns NULL if memory allocation failed.

SEE ALSO
     kdata_stddev_attach(3), kplot(3)

     Donald E. Knuth, The Art of Computer Programming: Seminumerical Algorithms,
     3rd Edition, Addison-Wesley, Volume 2, 232, Boston, 1998.

CAVEATS
     Each standard deviation bucket can process a maximum number of SIZE_MAX up-
     dates.

FreeBSD ports 15.quarterly	January 22, 2015	   KDATA_STDDEV_ALLOC(3)
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