MAX

The MAX function returns the value of the largest element of Array.

Syntax

Result = MAX( Array [, Max_Subscript] [, DIMENSION=value] [, MIN=variable] [, /NAN] [, SUBSCRIPT_MIN=variable])

Return Value

Return the largest array element value. The type of the result is the same as the type of Array.

Arguments

Array

The array to be searched.

Max_Subscript

A named variable that, if supplied, is converted to a long integer containing the one-dimensional subscript of the maximum element. Otherwise, the system variable !C is set to the one-dimensional subscript of the maximum element.

Keywords

DIMENSION

Set this keyword to the dimension over which to find the maximum values of an array. If this keyword is not present or is zero, the maximum is found over the entire array and is returned as a scalar value. If this keyword is present and nonzero, the result is the "slice" of the input array that contains the maximum value element, and the return values for Result, Max_Subscript, MIN, and SUBSCRIPT_MIN will all be arrays of one dimension less than the input array. That is, if the dimensions of Array are N1, N2, N3, and DIMENSION=2, the dimensions of the result are (N1, N3), and element (i,j) of the result contains the maximum value of Array[i, *, j].

For example:

arr = FINDGEN(2,3,2) 
PRINT, arr 

IDL prints:

0.00000     1.00000 
2.00000     3.00000 
4.00000     5.00000 
 
6.00000     7.00000 
8.00000     9.00000 
10.0000     11.0000 
 
PRINT, MAX(arr, DIMENSION=2) 

IDL prints:

4.00000     5.00000 
10.0000     11.0000 
 
PRINT, MAX(arr, DIMENSION=1) 

IDL prints:

1.00000     3.00000     5.00000 
7.00000     9.00000     11.0000 

MIN

A named variable to receive the value of the minimum array element. If you need to find both the minimum and maximum array values, use this keyword to avoid scanning the array twice with separate calls to MAX and MIN.

NAN

Set this keyword to cause the routine to check for occurrences of the IEEE floating-point values NaN or Infinity in the input data. Elements with the value NaN or Infinity are treated as missing data. (See Special Floating-Point Values for more information on IEEE floating-point values.)

SUBSCRIPT_MIN

Set this keyword equal to a named variable that will contain the one-dimensional subscript of the minimum element, the value of which is available via the MIN keyword.

Thread Pool Keywords

This routine is written to make use of IDL's thread pool, which can increase execution speed on systems with multiple CPUs. The values stored in the !CPU system variable control whether IDL uses the thread pool for a given computation. In addition, you can use the thread pool keywords TPOOL_MAX_ELTS, TPOOL_MIN_ELTS, and TPOOL_NOTHREAD to override the defaults established by !CPU for a single invocation of this routine. See Thread Pool Keywords for details.

Examples

Example 1

This example prints the maximum value in an array, and the subscript of that value:

; Create a simple two-dimensional array: 
D = DIST(100) 
 
; Print the maximum value in array D and its linear subscript: 
PRINT, 'Maximum value in array D is:', MAX(D, I) 
PRINT, 'The subscript of the maximum value is', I 

IDL Output

Maximum value in array D is:      70.7107 
The subscript of the maximum value is        5050 

Example 2

To convert I to a two-dimensional subscript, use the commands:

IX = I MOD 100 
IY = I/100 
PRINT, 'The maximum value of D is at location ('+ STRTRIM(IX, 1) $ 
   + ', ' + STRTRIM(IY, 1) + ')' 

IDL Output

The maximum value of D is at location (50, 50) 

Version History

Introduced: Original

See Also

ARRAY_INDICES, MIN, WHERE