% At_f.m%% Adjoint for "scrambled Fourier" measurements.%% Usage: x = At_f(b, N, OMEGA, P)%% b - K vector = [real part; imag part]%% N - length of output x%% OMEGA - K/2 vector denoting which Fourier coefficients to use%         (the real and imag parts of each freq are kept).%% P - Permutation to apply to the input vector.  Fourier coeffs of%     x(P) are embedded.%     Default = 1:N (no scrambling).%% Written by: Justin Romberg, Caltech% Created: October 2005% Email: jrom@acm.caltech.edu%function x = At_f(b, N, OMEGA, P)if (nargin < 4),  P = 1:N;  endK = length(b);fx = zeros(N,1);fx(OMEGA) = sqrt(2)*b(1:K/2) + i*sqrt(2)*b(K/2+1:K);x = zeros(N,1);x(P) = sqrt(N)*real(ifft(fx));