This function takes two x and y vectors, and calculates the corresponding
6 Layman metrics based on these points. Note that for generality, the
original metrics of dC_range and dN_range have been renamed dX_range and
dY_range respectively. These modified names represent the x and y axes in
terms of the order in which the data have been entered, and relate typically
to how one plots the data. These x and y vectors could represent the means
of the group members comprising a community as is preferred under the SIBER
model framework. However, one could use them to calculate the point estimates
of the 6 Layman metrics for an entire group of data. In fact, you are free
to pass this function any set of x and y data you wish.