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//function [w] = blackmannuttall (m, opt)
//This function returns the filter coefficients of a Blackman-Nuttall window.
//Calling Sequence
//w = blackmannuttall (m)
//w = blackmannuttall (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 Blackman-Nuttall 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.
//Examples
//blackmannuttall(5,"symmetric")
//ans =
// 0.0003628
// 0.2269824
// 1.
// 0.2269824
// 0.0003628
function w = blackmannuttall (m, opt)
funcprot(0);
rhs= argn(2);
if (rhs < 1 | rhs > 2)
error("Wrong Number of input arguments");
end
if (~ (isscalar (m) & (m == fix (m)) & (m > 0)))
error ("blackmannuttall: M must be a positive integer");
end
N = m - 1;
if (rhs == 2)
select (opt)
case "periodic"
N = m;
case "symmetric"
N = m-1;
else
error ("nuttallwin: window type must be either periodic or symmetric");
end
end
if (m == 1)
w = 1;
else
a0 = 0.3635819;
a1 = 0.4891775;
a2 = 0.1365995;
a3 = 0.0106411;
// n = [-N/2:(m-1)/2]';
// w = a0 + a1.*cos(2.*%pi.*n./N) + a2.*cos(4.*%pi.*n./N) + a3.*cos(6.*%pi.*n./N);
n=[0:m-1]'
w = a0 - a1.*cos(2.*%pi.*n./N) + a2.*cos(4.*%pi.*n./N) - a3.*cos(6.*%pi.*n./N);
end
endfunction
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