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function M = fht(D, N, DIM)
// Description
// This function calculates the Fast Hartley transform of real input D.
// If D is a matrix, the Hartley transform is calculated along the columns by default.
// If N is specified, the first N elements along the specified dimension are used for the transform.
// If DIM is specified, the transform is calculated along the specified dimension.
// Calling Sequence
// M = fht (D)
// M = fht (D, N)
// M = fht (D, N, DIM)
// Parameters
// D: Input data (real matrix or vector).
// N: Number of elements of D to be used for the transform (optional).
// DIM: Dimension along which the transform is to be computed (optional).
// Examples
// fht(1:4)
// ans =
// 10 -4 -2 0
funcprot(0);
rhs = argn(2);
if rhs < 1 | rhs > 3 then
error("Wrong number of input arguments.")
end
// The fht will be calculated along the first non-singleton dimension of the array i.e along the columns by default.
dimension = size(D);
nsdim = 1;
for i = 1:length(dimension)
if dimension(i) ~= 1 then
nsdim = i;
break;
end
end
// Process input arguments
select(rhs)
case 1 then
M = fft(D, -1, nsdim);
case 2 then
if isempty(N) then
n = size(D, nsdim);
else
n = N;
end
new_size = size(D);
new_size(nsdim) = n;
D = resize_matrix(D, new_size);
M = fft(D, -1, nsdim);
case 3 then
if isempty(N) then
n = size(D, DIM);
else
n = N;
end
new_size = size(D);
new_size(DIM) = n;
D = resize_matrix(D, new_size);
M = fft(D, -1, DIM);
end
// Return real part of the result
M = real(M) - imag(M);
endfunction
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