IANAS, but the example is not linear in x. But you can pick one or more axes where it would be linear. In this case for y=a*sin(x)+bx^2, you set x'=sin(x) and x

IANAS, but the example is not linear in x. But you can pick one or more axes where it would be linear. In this case for y=a*sin(x)+bx^2, you set x'=sin(x) and x"=x^2 and plot y=ax'+ bx". You can also pick an arbitrary function for y and do a similar transformation.