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//filtord Filter order
//Calling Syntax
//n = filtord(b,a)
//n = filtord(sos)
//n = filtord(d)
//n = filtord(b,a) returns
//the filter order, n, for the causal rational
//system function specified by the numerator coefficients, b,
//and denominator coefficients, a.
//n = filtord(sos) returns
//the filter order for the filter specified by the second-order sections
//matrix, sos. sos is a K-by-6
//matrix. The number of sections, K, must be greater
//than or equal to 2. Each row of sos corresponds
//to the coefficients of a second-order filter. The ith
//row of the second-order section matrix corresponds to [bi(1)
//bi(2) bi(3) ai(1) ai(2) ai(3)].
//n = filtord(d) returns
//the filter order, n, for the digital filter, d.
//Use the function designfilt to
//generate d.
//Author: Parthasarathi Panda
//parthasarathipanda314@gmail.com
function m=filtord(varargin)
[nargout,nargin]=argn();
narginchk(1,2,argn(2));
if (nargin==2) then
a=varargin(1);
b=varargin(2);
if(length(b)==0) then
b=[0];
end
if length(a)==0 then
a=[0];
end
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
elseif (nargin==1) then
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
end
k=length(a);
order_a=0;
for i=k:-1:1
if (a(1,i)~=0) then
order_a=i;
break;
end
end
k=length(b);
order_b=0;
for i=[k:-1:1]
if (b(1,i)~=0) then
order_b=i;
break;
end
end
m=max(order_a,order_b)-1;
endfunction
function narginchk(l,h,eip)
if (eip<l) then
error("Too few input arguments");
end
if(eip>h) then
error("too many input arguments");
end
endfunction
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