Plotting a function directly from a text file

Question

Is there a way to plot a function based on values from a text file?

I know how to define a function in gnuplot and then plot it but that is not what I need. I have a

Answer 1

awk '/1/ {print "plot "$2"*x**2+"$3"*x+"$4}' | gnuplot -persist

Will select the line and plot it