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//islinphase Determine whether filter has linear phase
// Calling Syntax and Parameter description
//flag = islinphase(b,a)
//takes input as numerator and denumerator coefficint matrices and returns flag =1 if filter is linear phase else return flag = 0
//flag = islinphase(sos)
//takes input as K x 6 second order split (sos) matrix and returns flag =1 if filter is linear phase else returns flag =0
//flag = islinphase(...,tol)
// tol -->this takes tolerence in similarities between two numbers in phase respose
//Example :
//flag = islinphase([0 1 2 2 1 0],1)
//Output:
//flag =
// 1.
//conclusion : output of above example is flag = 1 means filter is linear phase which must be as example is of symmetric linear phase fir filter
//Author: Parthasarathi Panda
//parthasarathipanda314@gmail.com
function islin=islinphase(varargin)
[nargout,nargin]=argn();
if (nargin==2) then
v=size(varargin(1));
if (v(2)~=6) | (v(2)==6 & v(1)==1) then
a=varargin(1);
b=varargin(2);
if type(a)~=1 | type(b)~=1 then
error('check input type');
end
v=size(a);
if length(v)>2 then
error('check input dimension');
end
v=size(b);
if length(v)>2 then
error('check input dimension');
end
[n,k]=size(a);
if k==1 then
a=a';
elseif n~=1 then
error('check input dimension');
end
[n,k]=size(b);
if k==1 then
b=b';
k=n;
elseif n~=1 then
error('check input dimension');
end
tol=0;
else
sos=varargin(1);
if type(sos)~=1 then
error('check input dimension');
end
v=size(sos);
if length(v)>2 then
error('check input dimension');
end
if v(2)~=6 then
error('no. of columns must be 6');
end
a=1;b=1;
for i=[1:v(1)]
a=convol(a,sos(1:3));
b=convol(b,sos(4:6));
end
tol=varargin(3);
if (type(tol)~=1) then
error('check input type');
end
if (size(tol)~=[1,1]) then
error('check input dimension');
end
end
elseif (nargin==1) then
tol=0;
sos=varargin(1);
if type(sos)~=1 then
error('check input dimension');
end
v=size(sos);
if length(v)>2 then
error('check input dimension');
end
if v(2)~=6 then
error('no. of columns must be 6');
end
a=1;b=1;
for i=[1:v(1)]
a=convol(a,sos(1:3));
b=convol(b,sos(4:6));
end
elseif (nargin==3) then
a=varargin(1);
b=varargin(2);
if type(a)~=1 | type(b)~=1 then
error('check input type');
end
v=size(a);
if length(v)>2 then
error('check input dimension');
end
v=size(b);
if length(v)>2 then
error('check input dimension');
end
[n,k]=size(a);
if k==1 then
a=a';
elseif n~=1 then
error('check input dimension');
end
[n,k]=size(b);
if k==1 then
b=b';
k=n;
elseif n~=1 then
error('check input dimension');
end
tol=varargin(3);
if (type(tol)~=1) then
error('check input type');
end
if (size(tol)~=[1,1]) then
error('check input dimension');
end
else
error('no. of inputs not matching');
end
if length(b)==1 then
err=a-a($:-1:1);
maxerr=max(err.*conj(err));
if err<=tol then
islin=1;
else
islin=0;
end
else
islin=0;
end
endfunction
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