224 Spatial Point Patterns: Methodology and Applications with R
for example. To override this refusal, convert the objec t to a data frame using as.data.frame and
then use ‘[’: the result will be a da ta frame or a vector.
Commands designed for data frame s often wor k for "fv" objects as well. The functions head
and tail extract the top (first few rows) and bottom (last few rows) of a data frame. They also work
on "fv" objects: the result is a new "fv" object containing the function values for a short interval
of r values at the beginning or e nd of the range. The fu nction subset selects designated subsets of
a data frame using an elegant sy ntax (see pa ge 101 ) an d this also works on "fv" objects. To restrict
Ks to the range r ≤ 0.1 and rem ove ...