isamin, idamin, icamin, izamin 

Index of the element of a vector with minimum absolute value

FORMAT

  I{S,D,C,Z}AMIN (n, x, incx)

Function Value

  imin                integer*4

                      The index of the first element of the vector x such
                      that (X(1+(imin-1)*|incx|)) is the smallest in absolute
                      value of all elements of the vector.  If n<=0, imin
                      returns the value 0.

Arguments

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

  x                   real*4 | real*8 |  complex*8 |  complex*16
                      On entry, a one-dimensional array X of length at least
                      (1+(n-1)*|incx|), containing the elements of the 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.

Description

  These subprograms compute the index of the element of a  vector having the
  minimum absolute value. They determine the first integer i of the vector x
  such that: |x(i)| = MAX{|x(j)|, j = 1,2, ...,n}
  For complex vectors, each element x(j) is a complex number.  In this
  subprogram, the absolute value of a complex number is defined as the
  absolute value of the real part of the complex number plus the absolute
  value of the imaginary part of the complex number: |x(j)| = |a(j)| + |b(j)|
  = |(real)| + |(imaginary)|

  If incx = 0, the computation is a time-consuming way of setting imin = 1.

Example

  INTEGER*4 N, INCX, IMIN
  REAL*4 X(40)
  INCX = 2
  N = 20
  IMIN = ISAMIN(N,X,INCX)

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