/* nag_fft_real (c06eac) Example Program. * * Copyright 1990 Numerical Algorithms Group. * * Mark 1, 1990. * Mark 8 revised, 2004. */ #include #include #include #include int main(void) { Integer exit_status = 0, j, n, n2, nj; NagError fail; double *a = 0, *b = 0, *x = 0, *xx = 0; INIT_FAIL(fail); printf("nag_fft_real (c06eac) Example Program Results\n"); /* Skip heading in data file */ scanf("%*[^\n]"); while (scanf("%ld", &n) != EOF) { if (n > 1) { if (!(a = NAG_ALLOC(n, double)) || !(b = NAG_ALLOC(n, double)) || !(x = NAG_ALLOC(n, double)) || !(xx = NAG_ALLOC(n, double))) { printf("Allocation failure\n"); exit_status = -1; goto END; } } else { printf("Invalid n.\n"); exit_status = 1; } for (j = 0; j < n; j++) { scanf("%lf", &x[j]); xx[j] = x[j]; } /* Calculate transform */ /* nag_fft_real (c06eac). * Single one-dimensional real discrete Fourier transform */ nag_fft_real(n, x, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_fft_real (c06eac).\n%s\n", fail.message); exit_status = 1; goto END; } /* Calculate full complex form of Hermitian result */ a[0] = x[0]; b[0] = 0.0; n2 = (n-1)/2; for (j = 1; j <= n2; j++) { nj = n - j; a[j] = x[j]; a[nj] = x[j]; b[j] = x[nj]; b[nj] = -x[nj]; } if (n % 2 == 0) { a[n2+1] = x[n2+1]; b[n2+1] = 0.0; } printf("\nComponents of discrete Fourier transform\n"); printf("\n Real Imag \n\n"); for (j = 0; j < n; j++) printf("%3ld %10.5f %10.5f\n", j, a[j], b[j]); /* Calculate inverse transform */ /* nag_conjugate_hermitian (c06gbc). * Complex conjugate of Hermitian sequence */ nag_conjugate_hermitian(n, x, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_conjugate_hermitian (c06gbc).\n%s\n", fail.message); exit_status = 1; goto END; } /* nag_fft_hermitian (c06ebc). * Single one-dimensional Hermitian discrete Fourier * transform */ nag_fft_hermitian(n, x, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_fft_hermitian (c06ebc).\n%s\n", fail.message); exit_status = 1; goto END; } printf("\nOriginal sequence as restored by inverse transform\n"); printf("\n Original Restored\n\n"); for (j = 0; j < n; j++) printf("%3ld %10.5f %10.5f\n", j, xx[j], x[j]); END: if (a) NAG_FREE(a); if (b) NAG_FREE(b); if (x) NAG_FREE(x); if (xx) NAG_FREE(xx); } return exit_status; }