function error2bar(x,ex,y,ey)
% plots errorbars with x +/- ex, y +/x ey  
%(ex and ey are absolute, not %, errors)
% all inputs must be row vectors
% Charlie Sullivan, 7/99

xe = [1; 1; 1; 1 ; 1; 1]*x+[-1; 1; 0; 0; 1; -1]*ex;
ye = [1; 1; 1; 1 ; 1; 1]*y+[-1; -1; -1; 1; 1; 1]*ey;

plot(x,y,'og',xe,ye,'-r')