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/* Description
Calculates the two-dimensional discrete Fourier transform of A using a Fast Fourier Transform algorithm.
It performs two-dimentional FFT on the matrix A. You can use the variables m and n to specify the number of rows and columns
of A that you want to use. If either of these variables is larger than the size of A,
then A will be resized, and zeros will be added as padding.
If A is a multi-dimensional matrix, the function will treat each two-dimensional sub-matrix of A separately.
Calling Sequence
fft21 (A)
fft21 (A, m, n)
Parameters
A: input matrix
m: number of rows of A to be used
n: number of columns of A to be used
Examples
A = [1 2 3; 4 5 6; 7 8 9]
m = 4
n = 4
fft21 (A, m, n)
ans =
45 + 0i -6 - 15i 15 + 0i -6 + 15i
-18 - 15i -5 + 8i -6 - 5i 5 - 4i
15 + 0i -2 - 5i 5 + 0i -2 + 5i
-18 + 15i 5 + 4i -6 + 5i -5 - 8i */
function res = fft21 (A, m, n)
funcprot(0);
lhs = argn(1)
rhs = argn(2)
if (rhs < 1 | rhs > 3)
error("Wrong number of input arguments.")
end
siz=size(A)
len=length(siz)
select(rhs)
case 1 then
if len>2 then
last_dim=siz(len)
else
last_dim=1
end
res=[]
for i=1:last_dim
res(:,:,i)=fft(A(:,:,i),-1)
end
case 2 then
error("Wrong number of input arguments.")
case 3 then
if len>2 then
last_dim=siz(len)
else
last_dim=1
end
res=[]
for i=1:last_dim
res(:,:,i)=fft(resize_matrix(A(:,:,i),m,n),-1)
end;
end
endfunction
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