% --- start of displayed preamble in the book --- input graph % --- end of displayed preamble in the book --- defaultfont:="ptmr8r"; warningcheck:=0; beginfig(1) path s; numeric x,y; draw begingraph(2.5in,1.75in); gdata ("students.dat",c, x:=(scantokens c1) * 12; y:=(scantokens c2); augment.s((x-5,0)-- (x-5,y)-- (x+5,y)-- (x+5,0)); if y < 0: glabel.top(c2,(x,0)); fi if y > 0: glabel.bot(c2,(x,0)); fi ); gfill s--cycle withcolor .5white; frame.llft; endgraph; endfig; end;