r8vec_expand_linear Subroutine

subroutine r8vec_expand_linear ( n, x, fat, xfat )

  !*****************************************************************************80
  !
  !! R8VEC_EXPAND_LINEAR linearly interpolates new data into an R8VEC.
  !
  !  Discussion:
  !
  !    This routine copies the old data, and inserts NFAT new values
  !    between each pair of old data values.  This would be one way to
  !    determine places to evenly sample a curve, given the (unevenly
  !    spaced) points at which it was interpolated.
  !
  !    An R8VEC is an array of double precision real values.
  !
  !  Example:
  !
  !    N = 3
  !    NFAT = 2
  !
  !    X(1:N)        = (/ 0.0,           6.0,             7.0 /)
  !    XFAT(1:2*3+1) = (/ 0.0, 2.0, 4.0, 6.0, 6.33, 6.66, 7.0 /)
  !
  !  Licensing:
  !
  !    This code is distributed under the GNU LGPL license. 
  !
  !  Modified:
  !
  !    10 October 2001
  !
  !  Author:
  !
  !    John Burkardt
  !
  !  Parameters:
  !
  !    Input, integer ( kind = 4 ) N, the number of input data values.
  !
  !    Input, real ( kind = 8 ) X(N), the original data.
  !
  !    Input, integer ( kind = 4 ) FAT, the number of data values to interpolate
  !    between each pair of original data values.
  !
  !    Output, real ( kind = 8 ) XFAT((N-1)*(FAT+1)+1), the "fattened" data.
  !
  implicit none

  integer ( kind = 4 ) fat
  integer ( kind = 4 ) n

  integer ( kind = 4 ) i
  integer ( kind = 4 ) j
  integer ( kind = 4 ) k
  real    ( kind = 8 ) x(n)
  real    ( kind = 8 ) xfat((n-1)*(fat+1)+1)

  k = 0

  do i = 1, n - 1

     k = k + 1
     xfat(k) = x(i)

     do j = 1, fat
        k = k + 1
        xfat(k) = ( real ( fat - j + 1, kind = 8 ) * x(i)     &
             + real (       j,     kind = 8 ) * x(i+1) ) &
             / real ( fat     + 1, kind = 8 )
     end do

  end do

  k = k + 1
  xfat(k) = x(n)

  return
end subroutine r8vec_expand_linear