cout<<"The sum of 4 and 7 is: "<<sum(4,7)<<endl; cout<<"The sum of 4 ,7 and 9 is: "<<sum(4,7,9)<<endl; cout<<"The volume of a Cylinder of radius 3 and height 6 is ...

Note 1: The vast majority of the functions accept matrices only, not data.frames. Note 2: Do not have matrices or vectors with have missing data (i.e NAs). We do no check about them and C++ internally ...