\newcount\arcircdiam
\newcount\ardeltax
\newcount\ardeltay
\newcount\arrowlength
\newcount\xarslope\newcount\yarslope
\newcount\xarslopesign\newcount\yarslopesign
\def\setdelta#1#2{\global\ardeltax=#1\global\ardeltay=#2%
  \global\multiply\ardeltax by\arcircdiam\global\divide\ardeltax by 2000%
  \global\multiply\ardeltay by\arcircdiam\global\divide\ardeltay by 2000}
\def\arrowcircle#1#2#3#4#5#6{%
  %draws vector from edge of circle of diam 15  
  \ifnum#3<0\global\xarslopesign=-1\global\xarslope=-#3
     \else\global\xarslopesign=1\global\xarslope=#3\fi\relax
  \ifnum#4<0\global\yarslopesign=-1\global\yarslope=-#4
     \else\global\yarslopesign=1\global\yarslope=#4\fi\relax
  \global\arcircdiam=#5
  \ifcase\xarslope\ifnum\yarslope=1\setdelta{0}{1000}%		0 1
        \else\setdelta{0}{0}\fi\relax%				error
     \or\ifcase\yarslope\setdelta{1000}{0}%			1 0
        \or\setdelta{707}{707}%					1 1
        \or\setdelta{447}{894}%					1 2
        \or\setdelta{316}{949}%					1 3
        \or\setdelta{243}{970}%					1 4
        \else\setdelta{0}{0}\fi\relax%				error
     \or\ifnum\yarslope=1\setdelta{894}{447}%			2 1
        \else\ifnum\yarslope=3\setdelta{555}{832}%		2 3
        \else\setdelta{0}{0}\fi\fi\relax%			error
     \or\ifnum\yarslope=1\setdelta{949}{316}%			3 1
        \else\ifnum\yarslope=2\setdelta{832}{555}%		3 2
        \else\ifnum\yarslope=4\setdelta{600}{800}%		3 4
        \else\setdelta{0}{0}\fi\fi\fi\relax%			error
     \or\ifnum\yarslope=1\setdelta{970}{243}%			4 1
        \else\ifnum\yarslope=3\setdelta{800}{600}%		4 3
        \else\setdelta{0}{0}\fi\fi\relax%			error
     \else\setdelta{0}{0}\fi\relax%				error
  \arrowlength=#6
  \advance\arrowlength by -\ardeltax\advance\arrowlength by -\ardeltax
  \multiply\ardeltax by\xarslopesign\advance\ardeltax by#1
  \multiply\ardeltay by\yarslopesign\advance\ardeltay by#2
  \put(\ardeltax,\ardeltay){\vector(#3,#4){\arrowlength}}}
\def\labeledcircle#1#2#3#4{\newcount\lcbot\newcount\lcleft\lcleft=#3%
   \put(#1,#2){\circle{#3}}%
   \divide\lcleft by -2\lcbot=\lcleft\advance\lcleft by#1%
   \advance\lcbot by #2%
   \put(\lcleft,\lcbot){\makebox(#3,#3){#4}}\relax}
%%%%%%%%%% THE END %%%%%%%%%%%%%%%%%%%%%%%