function sv = ESLselect(v,sy,dw,df)%sv = ESLselect(v,sy,dw,df)	Select the elements of a multi-element%DAC to minimize the selection error, subject to the constraint that %the nominal DAC output is v, i.e. v = sv'*dw.%df is a vector of dac error factors. de is defined s.t. df'*de = 0.%Assume that the preferred usage order is that given by dw.% Go through sv possibilities one by one, until one which meets the% v = sv'*dw constraint is found.if v<0 | v>sum(dw)    error('v argument is invalid (too large or too small)');endn = length(dw);sv = zeros(n,1);if v==0; return; end;[junk possibilities] = sort(-sy); 	%Determine the element priority% Code to speed up selection in the usual case where all% DAC elements are weighted at one. Suggested by J. A. Cherry, 5-Mar-97if dw==ones(n,1);    sv(possibilities(1:v)) = ones(1,v);    return;end;i = 1;				% Selection levelpointer = 1;			% Array of pointers to selected elementsselected = [];			% Selected elementswhile 1    while pointer(i)>n;	% backtrack	i = i-1;	if i==0	    break;	%failure!	end	pointer(i) = pointer(i)+1;	selected = selected(1:i);    end    selected(i) = possibilities(pointer(i));    dv = sum(dw(selected));    if dv==v	break;		%success!    elseif dv<v	% Proceed to the next level of selection	pointer(i+1) = pointer(i)+1;	i = i+1;    else	% Try the next element at the current level.	pointer(i) = pointer(i)+1;    endendsv(selected) = ones(1,length(selected));