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function varargout = alignsignals(x,y,varargin)
//This function aligns the two input signals.
//
//Syntax
//[Xa Ya] = ALIGNSIGNALS(X,Y)
//[Xa Ya] = ALIGNSIGNALS(X,Y,MAXLAG)
//[Xa Ya] = ALIGNSIGNALS(X,Y,MAXLAG,1)
//[Xa Ya D] = ALIGNSIGNALS(...)
//
//Description
//[Xa Ya] = ALIGNSIGNALS(X,Y) aligns the two vectors X and Y by estimating
//the delay D between the two. If Y is delayed with respect to X, D is
// positive , and X is delayed by D samples. If Y is advanced with respect
// to X, D is negative, and Y is delayed by -D samples.
//
// [Xa Ya] = ALIGNSIGNALS(X,Y,MAXLAG) considers MAXLAG be the maximum correlation
// window size which is used to calculate the estimated delay D between X and Y.
// MAXLAG is an integer-valued scalar. By default, MAXLAG is equal to MAX(LX,LY)-1.
// If MAXLAG is empty ([]),then default value is considered. If MAXLAG
// is negative, it is replaced by its absolute value.
//
// [Xa Ya] = ALIGNSIGNALS(X,Y,MAXLAG,1) keeps the lengths of Xa
// and Ya the same as those of X and Y, respectively.
// Here, 1 implies truncation of the intermediate vectors.
// Input argument 4 is 0 implies truncation_off (no truncation).
// D is positive implies D zeros are pre-pended to X, and the last D samples of X are truncated.
// D is negative implies -D zeros are pre-pended to Y, and the last -D samples
// of Y are truncated. That means, when D>=Length(X), all samples of X are lost.
// Similarly, when -D>=Length(Y), all samples of Y are lost.
// Avoid assigning a specific value to MAXLAG when using the truncate=1 option, set MAXLAG to [].
//
// [Xa Ya D] = ALIGNSIGNALS(...) returns the estimated delay D.
//
// Examples
// X = [0 0 0 1 2 3 ];
// Y = [1 2 3 ];
// [Xa,Ya] = alignsignals(X,Y,[],1)
//
// Authors
// Pola Lakshmi Priyanka, IIT Bombay
// Check number of input arguments
[out_a,inp_a]=argn(0)
if inp_a<=1 | inp_a>4 then
error('comm:alignsignals: Invalid number of input arguments')
end
if out_a>3 then
error('comm:alignsignals: Invalid number of output arguments')
end
//Check input arguments
if (~or(type(x)==[1 5 8]) | ~isvector(x) )
error('comm:alignsignals:Input argument 1 should be a vector of numbers');
end
[row_x,col_x] = size(x);
len_x = length(x);
if (~or(type(y)==[1 5 8]) | ~isvector(y) )
error('comm:alignsignals:Input argument 2 should be a vector of numbers');
end
[row_y,col_y] = size(y);
len_y = length(y);
//Check for MaxLag
if inp_a==3 then
maxlag = varargin(1)
else
maxlag = max(len_x,len_y)-1; //Default value
end
if ~isempty(maxlag) then
if ( ~or(type(maxlag)==[1 5 8]) | ~isreal(maxlag) | length(maxlag)~=1 | ceil(maxlag)~=maxlag),
error('comm:alignsignals:Input argument 3 should be a scalar integer');
elseif (( isnan(maxlag)) | isinf(maxlag)),
error('comm:alignsignals:Input argument 3 can not be Inf or NAN');
end
else
maxlag = maxlag_default;
end
maxlag = double(abs(maxlag));
//Check for truncate
trunc_on=0;
if inp_a==4
if (varargin(2))
trunc_on=1;
end
end
// Estimate delay between X and Y.
if inp_a==2
d = finddelay(x,y);
else
d = finddelay(x,y,maxlag);
end
if d == 0 // X and Y are already aligned.
varargout(1) = x;
varargout(2) = y;
elseif d > 0 // Y is estimated to be delayed with respect to X.
if row_x>1 // X is entered as a column vector.
if trunc_on==0
varargout(1) = [zeros(d,1) ; x];
else
if d>=row_x
warning('comm:alignsignals:firstInputTruncated');
varargout(1) = zeros(row_x,1);
else
varargout(1) = [zeros(d,1) ; x(1:len_x-d)];
end
end
else // X is entered as a row vector.
if trunc_on==0
varargout(1) = [zeros(1,d) x];
else
if d>=col_x
warning('comm:alignsignals:firstInputTruncated');
varargout(1) = zeros(1,col_x);
else
varargout(1) = [zeros(1,d) x(1:len_x-d)];
end
end
end
varargout(2) = y;
else // X is estimated to be delayed with respect to Y.
varargout(1) = x;
if row_y>1 // Y is entered as a column vector.
if trunc_on==0
varargout(2) = [zeros(-d,1) ; y];
else
if (-d)>=row_y
warning('comm:alignsignals:secondInputTruncated');
varargout(2) = zeros(row_y,1);
else
varargout(2) = [zeros(-d,1) ; y(1:len_y-(-d))];
end
end
else // Y is entered as a row vector.
if trunc_on==0
varargout(2)= [zeros(1,-d) y];
else
if (-d)>=col_y
warning('comm:alignsignals:secondInputTruncated');
varargout(2) = zeros(1,col_y);
else
varargout(2) = [zeros(1,-d) y(1:len_y-(-d))];
end
end
end
end
varargout(3) = d;
endfunction
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