synchronous_average.m

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function m=synchronous_average(x,T)
%
% SYNCHRONOUS_AVERAGE
%              calculate the synchronous average of the signal x
%              with period T
%
% USAGE
%              m=synchronous_average(x,T)
%
%              if T is a scalar, then T defined the fundamental
%              cyclic period
%
%              if T is a vector, then T defines a series of once
%              per revolution impulses

% File: synchronous_average.m
% Last Revised: 24/11/97
% Created: 24/11/97
% Author: Andrew C. McCormick
% (C) University of Strathclyde


% Simple error checks
if nargin~=2
  error('Incorrect number of arguments for function synchronous_average');
end
if T(1)<1
  error('Synchronous period must be larger than 1 in function synchronous average');
end



% Remove excess samples due to non-integer sampling
if length(T)==1
  % remove jitter samples if non-integer T
  if T~=floor(T)
    cp=1;np=1;
    while cp+T<length(x)
      cp=cp+floor(T);
      np=np+T;
      if (np-cp)>1
	x=[x(1:cp-1) x(cp+1:length(x))];
	np=np-1;
      end
    end
  end
  n=floor((length(x)-1)/T);
else
  % extract time series correlated with periodic pulses
  rot_positions=T;
  T=floor(median(diff(rot_positions)));
  nx=[];
  n=length(rot_positions)-2;
  for k=1:n;
    cp=rot_positions(k);
    nx=[nx; x(cp:cp+T-1)];
  end
  x=nx;
end

temp=zeros(floor(T),n);
t=(1:floor(T)*n);
temp(:)=x(t);
m=mean(temp');