sfct, dfct 

Fast cosine transform in one dimension

FORMAT

  status = {S,D}FCT

  (direction, in, out, n, type, stride)

Arguments

  direction           character*(*)
                      Specifies the operation as either the forward or
                      inverse transform. Use Use 'B' or

  in, out              real*4 | real*8
                      Both the arguments are one-dimensional arrays.  The
                      input and output arrays can be the same array. The IN
                      array contains the data to be transformed. The OUT
                      array contains the transformed data.  For type-I FCT,
                      the length of the IN,OUT array must must be

  n                   integer*4
                      Specifies the size of the transform. The minimum size
                      of the IN, OUT array is n; where n
                       and even.

  type                integer*4
                      Specifies the type of the Cosine transform desired.
                      Currently only type-1 and type-2 transforms are
                      supported.

  stride              integer*4
                      Specifies the distance between consecutive elements in
                      the IN and OUT arrays. The distance must be at least 1.

Description

  The _FCT functions compute the fast Cosine transform of one-dimensional
  data in one step.

Return Values

  0                  DXML_SUCCESS()

  4                  DXML_ILL_N_IS_ODD()

  8                  DXML_ILL_N_RANGE()

  12                 DXML_INS_RES()

  13                 DXML_BAD_STRIDE()

  15                 DXML_BAD_DIRECTION_STRING()

  17                 DXML_OPTION_NOT_SUPPORTED()

Example

  INTEGER*4 N
  PARAMETER (N=1024)
  INCLUDE 'CXMLDEF.FOR'
  INTEGER*4 STATUS
  REAL*8 C(0:N),D(0:N)
  REAL*4 E(1:N-1),F(1:N-1)
  STATUS = DFCT('F',C,D,N,1,1)
  STATUS = DFCT('B',D,C,N,1,1)
  STATUS = SFCT('F',E,F,N,2,1)
  STATUS = SFCT('B',F,E,N,2,1)

  This FORTRAN code computes the following:

  •  Forward Type-1 Cosine transform of the real sequence C to real sequence
     D.

  •  Backward Type-1 Cosine transform of the real sequence D to real sequence
     C.

  •  Forward Type-2 Cosine transform of the real sequence E to real sequence
     F.

  •  Backward Type-2 Cosine transform of the real sequence F to real sequence
     E.