Language Reference

PRODUCT(ARRAY, DIM, MASK) or PRODUCT(ARRAY, MASK)

Multiplies together all elements in an entire array, or selected elements from all vectors along a dimension.

ARRAY

is an array with a numeric data type.

DIM (optional)

is an integer scalar in the range 1 <= DIM <= rank(ARRAY).

MASK (optional)

is a logical expression that conforms with ARRAY in shape. If MASK is a scalar, the scalar value applies to all elements in ARRAY.

Class

Transformational function

Result Value

If DIM is present, the result is an array of rank rank(ARRAY)-1 and the same data type as ARRAY. If DIM is missing, or if MASK has a rank of one, the result is a scalar.

The result is calculated by one of the following methods:

Method 1:

If only ARRAY is specified, the result is the product of all its array elements. If ARRAY is a zero-sized array, the result is equal to one.

Method 2:

If ARRAY and MASK are both specified, the result is the product of those array elements of ARRAY that have a corresponding true array element in MASK. If MASK has no elements with a value of .TRUE., the result is equal to one.

Method 3:

If DIM is also specified, the result value equals the product of the array elements of ARRAY along dimension DIM that have a corresponding true array element in MASK.

+---------------------------------Fortran 95---------------------------------+

Because both DIM and MASK are optional, various combinations of arguments are possible. When the -qintlog option is specified with two arguments, the second argument refers to one of the following:

• MASK if it is an array of type integer, logical, byte or typeless
• DIM if it is a scalar of type integer, byte or typeless
• MASK if it is a scalar of type logical

+-----------------------------End of Fortran 95------------------------------+

Examples

Method 1:

! Multiply all elements in an array.
       RES = PRODUCT( (/2, 3, 4/) )
! The result is 24 because (2 * 3 * 4) = 24.
 
! Do the same for a two-dimensional array.
       RES = PRODUCT( (/2, 3, 4/), (/4, 5, 6/) )
! The result is 2880.  All elements are multiplied.

Method 2:

! A is the array (/ -3, -7, -5, 2, 3 /)
! Multiply all elements of the array that are > -5.
       RES = PRODUCT(A, MASK = A .GT. -5)
! The result is -18 because (-3 * 2 * 3) = -18.

Method 3:

! A is the array | -2  5  7 |
!                |  3 -4  3 |
! Find the product of each column in A.
       RES = PRODUCT(A, DIM = 1)
! The result is | -6 -20 21 | because (-2 * 3) =  -6
!                                    ( 5 * -4 ) = -20
!                                    ( 7 *  3 ) = 21
 
! Find the product of each row in A.
       RES = PRODUCT(A, DIM = 2)
! The result is | -70 -36 |
! because (-2 *  5 * 7) = -70
!          (3 * -4 * 3) = -36
 
! Find the product of each row in A, considering
! only those elements greater than zero.
       RES = PRODUCT(A, DIM = 2, MASK = A .GT. 0)
! The result is | 35 9 | because ( 5 * 7) = 35
!                                 (3 * 3) =  9