#### Description:

The supplied Fourier
coefficients in X and Y are replaced by the corresponding spatial data obtained by doing an inverse
Fourier transform. See the forward FFT routine PDA_NFFTF for more details.

#### Invocation

CALL
PDA_NFFTB( NDIM, DIM, X, Y, WORK, ISTAT )

#### Arguments

##### NDIM = INTEGER (Given)

The number of dimensions. This should be no more than 20.

##### DIM( NDIM ) = INTEGER
(Given)

The size of each dimension.

##### X( * ) = REAL (Given and Returned)

Supplied
holding the real parts of the Fourier coefficients. Returned holding the real parts of the spatial
data. The array should have the number of elements implied by NDIM and DIM.

##### Y( *
) = REAL (Given and Returned)

Supplied holding the imaginary parts of the Fourier
coefficients. Returned holding the imaginary parts of the spatial data. The array should have
the number of elements implied by NDIM and DIM.

##### WORK( * ) = REAL (Given and
Returned)

A work array. This should have at least ( 6*DimMax + 15 ) elements where
DimMax is the maximum of the values supplied in DIM.

##### ISTAT = INTEGER (Returned)

If the value of NDIM is greater than 20 or less than 1, then ISTAT is returned equal to 1,
and the values in X and Y are left unchanged. Otherwise, ISTAT is returned equal to 0.

#### Implementation Status:

A double precision version PDA_DNFFTB of the routine exists.