sscal1d(3F)

NAME
     sscal1d, dscal1d - scales a 1D real sequence.

SYNOPSYS
     Fortran :
     subroutine sscal1d( n, alpha, array, inc)
          integer            n, inc
          real               alpha, array(0:(n-1)*inc)
     subroutine dscal1d( sign, n, p, array, inc, lda)
          integer            n, inc
          real*8             alpha, array(0:(n-1)*inc)

     C :
     #include <fft.h>
     int sscal1d ( int n, float alpha, float *array, int inc);
     int dscal1d ( int n, double alpha, double *array, int inc);


DESCRIPTION
     sscal1d and dscal1d scale a 1D real sequence of N samples.
     The Fourier Transforms are not normalized so the succession Direct-
     Inverse transform scales the input data by a factor equal to the size of
     the transform.  sscal1d or dscal1d may be used to scale back the result.

PARAMETERS
     N Integer, the number of samples in each sequence.
     Unchanged on exit.

     P Integer, the number of sequences.  Unchanged on exit.

     Alpha scaling floating point value.

     ARRAY Array containing the samples of the sequence to be scaled (in
     place).

     INC Integer, increment between two consecutive elements of a sequence.
     Unchanged on exit.

     LDA Integer, leading dimension: increment between the first samples of
     two consecutive sequences.  Unchanged on exit.


Example of Calling Sequence
     Given a 1024 real values sequence.  We successively apply a Direct
     Fourier Transform, an Inverse Fourier Trasnform and finally scale back
     the result by a factor 1/N (1/1024.)-
     This sequence DirectFFT-InverseFFT-Scaling is equivalent to the identity
     operator and the final sequence should be equal (with round-off
     precision) to the initial sequence.
     Elements of each sequence are stored with increment (stride) 1.
     Fortran
          real array(0:1024-1), coeff(1024+15)
         call scfft1dui( 1024, coeff)
          call scfft1du( -1, 1024, array, 1, coeff)
          call scfft1du(  1, 1024, array, 1, coeff)
          call sscal1d( 1024, (1./real(1024)), array,1)

     C
          #include <fft.h>
          float array[1024], *coeff;
          coeff = scfft1dui( 1024, NULL);
          scfft1du( -1, 1024, array, 1, coeff);
          csfft1du(  1, 1024, array, 1, coeff);
          sscal1d( 1024, 1./(float)1024, array, 1);

     NOTE_1 : The Direct and Inverse transforms should use opposite signs -
     Which one is used (+1 or -1) for Direct transform is just a matter of
     convention-

     NOTE_2 : The Fourier Transforms are not normalized so the succession
     Direct-Inverse transform scales the input data by a factor equal to the
     size of the transform.

SEE ALSO
     fft, scfft1dui, dzfft1dui, scfft1du, dzfft1du, csfft1du, zdfft1du,
     sprod1du, dprod1du