我的程序如下，但是第二个曲线为何不显示虚线呢？

proc fcmp outlib=sasuser.funcs.math_stat;

  function g(u);
    if (u le  -0.25) then return (2*log((1+0.25*0.25)/(1+1.25*1.25)));
    if (u ge   1.25) then return (2*log((1+1.25*1.25)/(1+0.25*0.25)));
      else return(2*log((1+u*u)/(1+(u-1)*(u-1))));
  endsub;
run;

proc fcmp outlib=sasuser.funcs.math_stat;

  function f(u);
    return(2*log((1+u*u)/(1+(u-1)*(u-1))));
  endsub;
run;

options cmplib =sasuser.funcs;
data a;
do x=-5 to 5 by 0.01;
l=f(x);
lstar=g(x);
output;
end;
run;

proc gplot data=a;
plot l*x=1 lstar*x=2/overlay;
symbol1 i=join v=none;
symbol2 line=3;
label l='lr';
run;