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### CGPERCENTILES

CGPERCENTILES
This program calculates user-specified percentiles of a data set.
A percentile is the value of a variable below which a certain percent
of observations fall. In other words, 75% of the values in a data set
fall below the 75th percentile of the data. Computing percentiles is
really nothing more than counting in a sorted input array. A box-and-whisker
plot usually will display the 25th, 50th, and 75th percentiles.

A `commercial version <http://www.idlcoyote.com/coyotestore/index.php?main_page=product_info&cPath=2&products_id=196>`
of this program, containing a DIMENSION keyword, can be purchased from the Coyote Store. The
DIMENSION keyword allows the user to calculate the percentiles over a particular dimension
of a multi-dimensional data set.

Math

## Returns

The return value is either a scalar or vector of data values corresponding to
the number of percentiles asked for with the `Percentiles` keyword, or a -1 if
there is an error in the program.

## Params

data: in, required
The data from which percentiles are desired. A vector or an array.

## Keywords

percentiles: in, optional, type=float
Set this keyword to a scalar or vector of values between 0.0 and 1.0
to indicate the percentile desired. A value of 0.5 indicates the 50th
percentile. Default value is [0.25, 0.50, 0.75].

## Examples

To return percentile values for 0.25, 0.50, and 0.75 of a data set::
IDL> data = Randomu(3L, 100) * 100
IDL> Print, cgPercentiles(data, Percentiles=[0.25, 0.5, 0.75])
27.4920 45.3172 69.3138

## Author

FANNING SOFTWARE CONSULTING::
David W. Fanning
1645 Sheely Drive
Fort Collins, CO 80526 USA
Phone: 970-221-0438
E-mail: david@idlcoyote.com
Coyote's Guide to IDL Programming: http://www.idlcoyote.com

## History

Change History::
Written, 3 June 2013 by David W. Fanning.