Try out NAG Library functions
Explore NAG maths and stats routines with interactive demos
Single one-dimensional complex discrete Fourier transform, complex data type
Fast Fourier Transform | FFT | Fourier transforms, complex
This example reads in a sequence of complex data values and prints their discrete Fourier transform (as computed by C06PCF with ). It then performs an inverse transform using C06PCF with , and prints the sequence so obtained alongside the original data values.
Program c06pcfe ! C06PCF Example Program Text ! Mark 26 Release. NAG Copyright 2016. ! .. Use Statements .. Use nag_library, Only: c06pcf, nag_wp ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Integer :: ieof, ifail, j, n ! .. Local Arrays .. Complex (Kind=nag_wp), Allocatable :: work(:), x(:), xx(:) ! .. Executable Statements .. Write (nout,*) 'C06PCF Example Program Results' ! Skip heading in data file Read (nin,*) loop: Do Read (nin,*,Iostat=ieof) n If (ieof<0) Then Exit loop End If Allocate (work(2*n+15),x(0:n-1),xx(0:n-1)) Read (nin,*) x(0:n-1) xx(0:n-1) = x(0:n-1) ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 Call c06pcf('F',x,n,work,ifail) Write (nout,*) Write (nout,*) 'Components of discrete Fourier transform' Write (nout,*) Write (nout,*) ' Real Imag' Write (nout,*) Do j = 0, n - 1 Write (nout,99999) j, x(j) End Do Call c06pcf('B',x,n,work,ifail) Write (nout,*) Write (nout,*) 'Original sequence as restored by inverse transform' Write (nout,*) Write (nout,*) ' Original Restored' Write (nout,*) ' Real Imag Real Imag' Write (nout,*) Do j = 0, n - 1 Write (nout,99999) j, xx(j), x(j) End Do Deallocate (work,x,xx) End Do loop 99999 Format (1X,I5,2(:,5X,'(',F8.5,',',F8.5,')')) End Program c06pcfe