function o = interp(tr,or,t);
% o = interp(tr,or,t);
% does interpolation and extrapolation to target (tr,or)
%
%This is the same as Rich Muller's interp.m, but now Matlab 
%has come out with a function of their own called interp.

% find range k1,k2 for which ordinary interp1 works ok
	nr = length(tr);
	n  = length(t);
	tmin = tr(1);
	tmax = tr(nr);
	for k = 1:n;
		if t(n-k+1) >= tmin; k1 = n-k+1; end;
		if t(k)     <= tmax; k2 = k;     end;
		end;
o = zeros(n,1);
o(k1:k2) = interp1(tr,or,t(k1:k2));

% extrapolate outside the range k1:k2
if k1>1
	m = (or(2)-or(1))/(tr(2)-tr(1));	% beginning slope
	o(1:k1-1) = or(1) - m*(tr(1)-t(1:k1-1));
	end;
if k2<n;
	m = (or(nr)-or(nr-1))/(tr(nr)-tr(nr-1));	% end slope
	o(k2+1:n) = or(nr) + m*(t(k2+1:n)-tr(nr));	% this line is wrong
	end;