Name

ismax, idmax − Index of the real vector element with maximum value

FORMAT

I{S,D}MAX (n, x, incx)

Function Value

imaxinteger∗4

The index of the first element of the real vector x such that X(1+(imax-1)∗|incx|) is the largest of all elements of the vector. 
If n<=0, imax returns the value 0. 

Arguments

ninteger∗4
On entry, the number of elements in the vector x.
On exit, n is unchanged. 

xreal∗4 | real∗8
On entry, a one-dimensional array X of length at least (1+(n-1)∗|incx|), containing the elements of the real vector x.
On exit, x is unchanged. 

incxinteger∗4
On entry, the increment for the array X.
If incx > 0, vector x is stored forward in the array, so that x(i) is stored in location X(1+(i-1)∗incx). 
If incx < 0, vector x is stored backward in the array, so that x(i) is stored in location X(1+(n-i)∗|incx|). 
If incx = 0, only the first element is accessed. 
On exit, incx is unchanged. 

Description

ISMAX and IDMAX determine the first  integer i of vector x such that: x(i) = MAX{x(j), j = 1,2, ...,n}
If incx = 0, the computation is a time-consuming way of setting imax = 1.

Example

INTEGER∗4 N, INCX, IMAX
REAL∗4 X(40)
INCX = 2
N = 20
IMAX = ISMAX(N,X,INCX)

This FORTRAN example shows how to compute the index of the vector element with maximum value.