Such functions are called linear, for reasons that I'll explain soon enough (well, we generally want another condition for linear functions involving scalar multiples of the variable, but I'll ...

Now that you've got a good sense of how to 'speak' R, let's use it with linear regression to make distinctive predictions.

In this paper we treat of the number of solutions of certain piecewise linear (p.l.) equations and of necessary and sufficient conditions for a PL function to be a homeomorphism.