% --- start of displayed preamble in the book --- input graph def sq(expr x,y,num,perc) = gfill(x,y)--(x+10,y)--(x+10,y+10)--(x,y+10)--cycle withcolor (perc/100,perc/100,perc/100); glabel(num,(x+5,y+5)) if perc < 50: withcolor white fi; enddef; % --- end of displayed preamble in the book --- defaultfont:="ptmr8r"; warningcheck:=0; beginfig(1) defaultscale:=0.7; draw begingraph(70mm,24mm); setrange((20,10),(110,40)); autogrid(,); gdata ("pot.dat",c, sq((scantokens c1)*10,(scantokens c2)*10, c3, (scantokens c4));); endgraph; endfig; end;