set y2label "26-2x"
set y2tics
set ytics nomirror
plot "a.dat" u 1:2 w l axis x1y1 t "x^2","a.dat" u 1:3 w l axis x1y2 t "26-2x"
效果如图：
生成"a.dat"的Fortran程序：
program HelloWorld
integer i
real x(40),y1(40),y2(40)
OPEN(10,file="a.dat")
write(10,200)"#x","y1","y2"
200 format(3A15)
do i=1,40
x(i)=(i-1)*0.1
y1(i)=x(i)**2
y2(i)=26.0-2.0*x(i)
write(10,*)x(i),y1(i),y2(i)
end do
CLOSE(10)
STOP
end