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function w = welchwin (m, opt)
//This function returns the filter coefficients of a Welch window.
//Calling Sequence
//w = welchwin (m)
//w = welchwin (m, opt)
//Parameters
//m: positive integer value
//opt: string value, takes "periodic" or "symmetric"
//w: output variable, vector of real numbers
//Description
//This is an Octave function.
//This function returns the filter coefficients of a Welch window of length m supplied as input, to the output vector w.
//The second parameter can take the values "periodic" or "symmetric", depending on which the corresponding form of window is returned. The default is symmetric.
//For symmetric, the length should be an integer>2. For periodic, the length should be an integer>1.
//Examples
//welchwin(4,"symmetric")
//ans =
// 0.
// 0.8888889
// 0.8888889
// 0.
rhs = argn(2)
if(argn(2)<1 | argn(2)>2)
error("Wrong number of input arguments.")
end
if ((~isscalar (m) & (m == fix (m)) & (m > 0))) then
error (" M must be a positive integer");
end
N = (m - 1) / 2;
mmin = 3;
if argn(2)==2 then
select (opt)
case "periodic"
N = m / 2;
mmin = 2;
case "symmetric"
N = (m - 1) / 2;
else
error ("window type must be either periodic or symmetric");
end
end
if (m < mmin)
error ('M must be an integer greater than mmin');
end
n = [0:m-1]';
w = 1 - ((n-N)./N).^2;
endfunction
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