C06FJF is the NAG routine for finding the FFT of an N-dimensional array of complex data values. The routine performs a forward transformation. To do an inverse transform the complex conjugate of the input data is taken before calling C06FJF (using C06GCF), and the complex conjugate of the output data is taken on return from C06FJF.
There are no equivalent routines in FFTPACK as found in NETLIB. PDA_DNFFTF and PDA_DNFFTB have been written, which do the equivalent of C06FJF. These routines are a bit different to genuine FFTPACK routines in that they do not need any initialisation, and use NAG format rather than native FFTPACK format for complex data arrays and Fourier coefficient arrays. Consequently, replacing C06FJF is a bit easier than replacing the one-dimensional routines.
The steps involved in replacing C06FJF calls with equivalent FFTPACK calls are listed separately for forward and inverse transforms.
PDA [1ex