I{S,D}MAX (n, x, incx)
imax integer*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.
n integer*4 On entry, the number of elements in the vector x. On exit, n is unchanged. x real*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. incx integer*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.
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.
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.