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| Syntax |
idft2d(z) |
| See Also | ifft2 , dft2d , idft |
M is the number of rows in
z and N is the number of columns in
z, the (m,n)-th
element of the return value is equal to
M N
1 ----- ----- { __ [ (i - 1) (m - 1) / M ] }
--- > > z exp{ +2 pi \/-1 [ + ] }
N M ----- ----- i,j { [ (j - 1) (n - 1) / N ] }
i = 1 j = 1
M and N are
2, 3, 5, and 7, the transform is done in order
(M)(N)[log(N) + log(M)] operations;
otherwise the transform is done in order
(M)(N)(N + M) operations.
M is 4, N is 2,
and the (4,1)-th and (4,2)-th elements of z
are one (the rest of the elements of z are zero).
The (m,n)-th element of the transform is therefore equal to
__ __
exp{+2 pi \/-1 [(m - 1)3/4]}/8 + exp{+2 pi \/-1 [(m - 1)3/4 + (n - 1)/2]}/8
__ __
exp{+2 pi \/-1 [(m - 1)3/4]} * ( 1 + exp{+2 pi \/-1 [(n - 1)/2]}) / 8
z = [{0, 0, 0, 1}, {0, 0, 0, 1}]
idft2d(z)
O-Matrix replies
{
[ (0.25,0) , (0,0) ]
[ (0,-0.25) , (0,0) ]
[ (-0.25,0) , (0,0) ]
[ (0,0.25) , (0,0) ]
}
ifft2 instead of idft2d.
If in Mlmode you enter
z = [0 0 0 1; 0 0 0 1]';
ifft2(z)
O-Matrix replies
{
[ (.25,0) , (0,0) ]
[ (0,-.25) , (0,0) ]
[ (-.25,0) , (0,0) ]
[ (0,.25) , (0,0) ]
}