NAME:		Statistics

AUTHOR INFO:	Anonymous, Stardent Computers
		email: avsmods@stardent.com

SOURCE FILE:	statistics.c

TYPE:		renderer

INPUTS:		field float

OUTPUTS:	formatted numerical text to standard-output

PARAMETERS:     None.

DESCRIPTION:
    STATISTICS is a field diagnostic and analysis module, similar to 
VOLSTAT, used to obtain global statistical information about field data.
This module scans the data in the volume, and produces a small table,
sent to stdout, usually into the window where avs was invoked, unless
redirected. A typical table looks like:

Field Statistics
===================
Dimensions:         628 184 (x4)
Min/Max:            0.000000 255.000000
Mean:               58.934429
Median:             0.000000
Standard Deviation: 76.030327
Skewness:           1.328104
Kurtosis:           0.686514

This table was generated from the following network:

	READ IMAGE	(read in stardent.x)
	     |
      FIELD TO FLOAT
	     | 
 	STATISTICS

The following information is provided:
DIMENSIONS:    	the dimensions of the field (with vector length, if applicable).
MIN/MAX:	the lowest and highest values in the data set.
MEAN:		the average of the data.
MEDIAN:		the center value of a sorted list of the data.
STANDARD DEVIATION: the square root of the sum of the squares of the
	        deviations.

The next two values, Skewness and Kurtosis, are values derived from
comparing the distribution of the values to an ideal Gaussian
distribution.

Skewness:	when positive, the right side of the distribution
		curve is "steeper" than the left, when negative, its
		the opposite.
Kurtosis:	when positive, the data is considered more "spikey",
		when negative, the data is considered to be more
		broadly distributed.

SEE ALSO:	DISPLAY HISTOGRAM, VOLSTAT (both in the User Module Library)

LIMITATIONS:	The computing of the median value requires sorting the
data which may be an expensive (timely) operation for large data sets.