MAXVAL(3I) Last changed: 1-6-98
NAME
MAXVAL - Returns the maximum value in an array
SYNOPSIS
MAXVAL ([ARRAY=]array [,[DIM=]dim] [,[MASK=]mask])
MAXVAL ([ARRAY=]array [,[MASK=]mask])
IMPLEMENTATION
UNICOS, UNICOS/mk, and IRIX systems
STANDARDS
Fortran 90
DESCRIPTION
The MAXVAL intrinsic function can be used for array reduction. It
returns the maximum value of the elements of array along dimension dim
corresponding to the true elements of mask. It accepts the following
arguments:
array Must be of type integer or real. It must not be scalar.
dim Must be a scalar integer value in the range 1 <= dim <= n,
where n is the rank of array. The corresponding actual
argument must not be an optional dummy argument. This
function does a check on dim when present.
mask This optional argument must be of type logical and must be
conformable with array.
MAXVAL is a transformational intrinsic function. The name of this
intrinsic cannot be passed as an argument.
NOTES
On UNICOS systems, both execution speed and the number of bits used in
mathematical operations are affected when compiling with
f90 -O fastint, which is the default setting. For more information,
see CF90 Commands and Directives Reference Manual, publication SR-
3901.
RETURN VALUES
The result is of the same type as array. It is scalar if dim is
absent or array has rank one. Otherwise, the result is an array of
rank n-1 and of shape
(d , d , ..., d , d , ..., d ),
1 2 dim-1 dim+1 n
where (d , d , ..., d )
1 2 n
is the shape of array.
The result of MAXVAL(array) has a value equal to the maximum value of
all the elements of array or has the value of the negative number of
the largest magnitude supported for numbers of the data type of array
if array is a zero-sized array.
The result of MAXVAL(array,MASK=mask) has a value equal to the maximum
value of all the elements of array corresponding to true elements of
mask or has the value of the negative number of the largest magnitude
supported for numbers of the data type of array if there are no true
elements.
If array has rank one, MAXVAL(array,dim[,mask]) has a value equal to
that of MAXVAL(array[,MASK=mask]). Otherwise, the value of element
(s , s , ..., s , s , ..., s )
1 2 dim-1 dim+1 n
of MAXVAL(array,dim[,mask]) is equal to
MAXVAL(array(s , s , ..., s , : , s , ..., s )
1 2 dim-1 dim+1 n
[, MASK=mask(s , s , ..., s , : , s , ..., s )]).
1 2 dim-1 dim+1 n
On UNICOS and UNICOS/mk systems, MAXVAL returns the value of
-HUGE(array) for all zero-sized arrays. On IRIX systems, MAXVAL
returns the value of -INFINITY for real, zero-sized arrays. A request
for interpretation of the Fortran 90 standard may change one of these
return values for a real array in a future release.
EXAMPLES
Example 1: The value of MAXVAL( (/ 1, 2, 3 /) ) is 3.
Example 2: Assume that C is the array [10,-100,10]. Then
MAXVAL(C, MASK=C .LT. 0.0) finds the maximum of the negative elements
of C (which is -100) and MAXVAL(C, MASK=C .GT. 10) returns a negative
number of the largest possible integer because there are no true
elements using the mask.
Example 3: Assume that B is the following array:
| 1 3 5 |
| 2 4 6 |
The following are true:
MAXVAL(B, DIM=1) is [2, 4, 6]
MAXVAL(B, DIM=2) is [5, 6]
MAXVAL(B) is 6
Example 4: Assume that N is the following array:
| 0 1 2 3 |
| 4 5 6 7 |
| 8 9 0 1 |
The following are true:
MAXVAL(N(2:3,2:4),MASK=N(2:3,2:4).NE.0) is 9
MAXVAL(N(2:3,2:4),DIM=1,N(2:3,2:4).NE.0) is [9, 6, 7]
MAXVAL(N(2:3,2:4),DIM=2,N(2:3,2:4).NE.0) is [7, 9]
SEE ALSO
Intrinsic Procedures Reference Manual, publication SR-2138, for the
printed version of this man page.
