RANKS

The RANKS function computes the magnitude-based ranks of a sample population X. Elements of identical magnitude "ties" are ranked according to the mean of the ranks that would otherwise be assigned.

This routine is written in the IDL language. Its source code can be found in the file ranks.pro in the lib subdirectory of the IDL distribution.

Syntax

Result = RANKS(X)

Return Value

The result is a vector of ranks equal in length to X.

Arguments

X

An n-element integer, single-, or double-precision floating-point vector. The elements of this vector must be in ascending order based on their magnitude.

Keywords

None.

Examples

; Define an n-element sample population:
X = [-0.8, 0.1, -2.3, -0.6, 0.2, 1.1, -0.3, 0.6, -0.2, 1.1, $
-0.7, -0.2, 0.6, 0.4, -0.1, 1.1, -0.3, 0.3, -1.3, 1.1]

; Allocate a two-column, n-row array to store the results:
array = FLTARR(2, N_ELEMENTS(X))

; Sort the sample population and store in the 0th column of ARRAY:
array[0, *] = X[SORT(X)]
; Compute the ranks of the sorted sample population and store in
; the 1st column of ARRAY:
array[1, *] = RANKS(X[SORT(X)])

; Display the sorted sample population and corresponding ranks
; with a two-decimal format:
PRINT, array, FORMAT = '(2(5x, f5.2))'

IDL prints:

-2.30      1.00 
-1.30      2.00 
-0.80      3.00 
-0.70      4.00 
-0.60      5.00 
-0.30      6.50 
-0.30      6.50 
-0.20      8.50 
-0.20      8.50 
-0.10     10.00 
 0.10     11.00 
 0.20     12.00 
 0.30     13.00 
 0.40     14.00 
 0.60     15.50 
 0.60     15.50 
 1.10     18.50 
 1.10     18.50 
 1.10     18.50 
 1.10     18.50

Version History


4.0	Introduced