set terminal latex
 set output   "f:xmplot.tex"
 set sample   500
 set xrange   [0:5]
 set yrange   [0:1]
 p(x) = (-3*x*x+12*x-7)/8
 f(x) = (x<1 ? 0 : (x>3 ? 0 : k(x) ) )
 plot f(x)