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C Library Functions  - medianval (3)

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NAME

medianval(3f) - [M_orderpack:MEDIAN] Returns median VALUE.

CONTENTS

Synopsis
Description
Options
Returns
Examples
Author
Maintainer
License

SYNOPSIS

Recursive Function MedianVal (INVALS) Result (RES_MED)

      ${TYPE} (kind=${KIND}),  Intent (In) :: INVALS(:)
      ${TYPE} (kind=${KIND})               :: RES_MED

Where ${TYPE}(kind=${KIND}) may be

o	Real(kind=real32)
o	Real(kind=real64)
o	Integer(kind=int32)

DESCRIPTION

Finds out and returns the median (((Size(INVALS)+1))/2^th value) of INVALS.

Internally, it uses the recursive procedure described in Knuth, The Art of Computer Programming, vol. 3, 5.3.3 .

The procedure is linear in time, and does not require to be able to interpolate in the set as the one used in ORDERVAL(3f)/ORDERLOC(3f). It also has better worst case behavior than ORDERVAL(3f)/ORDERLOC(3f), and is about 20% faster in average for random uniformly distributed values.

OPTIONS

INVALS	input array

RETURNS

RES_MED
	the median value of the array INVALS

EXAMPLES

Sample program:

   program demo_medianval
   ! return median value
   use M_orderpack, only : medianval
   implicit none
   character(len=*),parameter :: g=’(*(g0,1x))’
      write(*,g)’real   ’,&
      medianval( [80.0,70.0,20.0,10.0,1000.0] )
      write(*,g)’integer’,&
      medianval( [11, 22, 33, 44, 55, 66, 77, 88] )
      write(*,g)’double ’,&
      medianval( [11.0d0, 22.0d0, 33.0d0, 66.0d0, 77.0d0, 88.0d0] )
   end program demo_medianval

Results:

   real    70.00000
   integer 44
   double  33.00000000000000

AUTHOR

Michel Olagnon, 2000-2012

MAINTAINER

John Urban, 2022.04.16

LICENSE

CC0-1.0

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Nemo Release 3.1

medianval (3)

July 22, 2023

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