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/* Description
Calculates the inverse discrete Fourier transform of a matrix using Fast Fourier Transform algorithm.
The inverse FFT is calculated along the first non-singleton dimension of the array. Thus, inverse FFT is computed for each column of x.
n is an integer specifying the number of elements of x to use. If n is larger than dimention along. which the inverse FFT is calculated, then x is resized and padded with zeros.
Similarly, if n is smaller, then x is truncated.
dim is an integer specifying the dimension of the matrix along which the inverse FFT is performed.
Calling Sequence
ifft1 (x)
ifft1 (x, n)
ifft1 (x, n, dim)
Parameters
x: input matrix
n: Specifies the number of elements of x to be used
dim: Specifies the dimention of the matrix along which the inverse FFT is performed
Examples
x = [1 2 3; 4 5 6; 7 8 9]
n = 3
dim = 2
ifft1 (x, n, dim)
ans =
2.00000 + 0.00000i -0.50000 - 0.28868i -0.50000 + 0.28868i
5.00000 + 0.00000i -0.50000 - 0.28868i -0.50000 + 0.28868i
8.00000 + 0.00000i -0.50000 - 0.28868i -0.50000 + 0.28868i */
function res = ifft1 (x, n, dim)
funcprot(0);
lhs = argn(1)
rhs = argn(2)
if (rhs < 1 | rhs > 3)
error("Wrong number of input arguments.")
end
dimension = size(x);
nsdim = 1;
for i = 1:length(dimension)
if dimension(i) ~= 1 then
nsdim = i;
break;
end
end
select(rhs)
case 1 then
res=fft(x,1,nsdim)
case 2 then
if isempty(n) then
res=fft(x,1,nsdim)
else
dimension(nsdim)=n;
res=fft(resize_matrix(x,dimension),1,nsdim)
end
case 3 then
if isempty(n) then
res=fft(x,1,dim)
else
if (length(dimension) <dim )then
error("ifft1: DIM must be a valid dimension along which to perform FFT")
end
dimension(dim)=n;
res=resize_matrix(x,dimension);
res=fft(res,1,dim);
end
end
endfunction
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