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function w=blackman(N,sflag)
//Generates a Blackman window
//Calling Sequence
//w=blackman(N)
//w=blackman(N,sflag)
//Parameters
//N
//A positive integer describing the length of the blackman window
//sflag
//Specifies the type of blackman window desired. Can be 'symmetric' or 'periodic'
//Description
//w=blackman(N) returns an N-point symmetric Blackman window in a column vector w
//w=blackman(N,sflag)
//Returns an N point Blackman window using the type of sampling specified by sflag
//sflag can be either 'symmetric' (default) or 'periodic' (used in spectral analysis)
//Example
//w=blackman(4)
//w =
//
// - 1.388D-17
// 0.63
// 0.63
// - 1.388D-17
//Author
//Ankur Mallick
//References
//[1] Oppenheim, Alan V., Ronald W. Schafer, and John R. Buck. Discrete-Time Signal Processing. Upper Saddle River, NJ: Prentice Hall, 1999.
funcprot(0);
if(argn(2)<2)
sflag='symmetric'; //Default
end
if(argn(2)<1|argn(2)>2)
error('Incorrect number of input arguments.');
elseif(~isscalar(N)|N<=0|round(N)~=N)
error('N must be a positive integer')
elseif(sflag~='symmetric'&sflag~='periodic')
error('Sampling flag must be either symmetric or periodic');
elseif(N==1)
w=1; //Trivial case
else
flag=0;
if(sflag=='periodic')
N=N+1;
flag=1;
end
if(pmodulo(N,2)==1)
M=(N+1)/2; //odd
else
M=N/2; //even
end
n=0:1:M-1;
w1=0.42-0.5*cos(2*%pi*n/(N-1))+0.08*cos(4*%pi*n/(N-1));
p=2*M-N; //0 for N even, 1 for N odd
w=[w1, w1(M-p:-1:1)]';
if(flag==1)
//Periodic case
w(N)=[];
end
end
endfunction
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