improve docs; #2319

Author: edzer

R/arith.R

@@ -1,10 +1,10 @@
-#' S3 Ops Group Generic Functions for simple feature geometries
+#' Arithmetic operators for simple feature geometries
 #' @name Ops
 #'
 #' @param e1 object of class \code{sfg} or \code{sfc}
 #' @param e2 numeric, or object of class \code{sfg}; in case \code{e1} is of class \code{sfc} also an object of class \code{sfc} is allowed
 #'
-#' @details in case \code{e2} is numeric, +, -, *, /, %% and %/% add, subtract, multiply, divide, modulo, or integer-divide by \code{e2}. In case \code{e2} is an n x n matrix, * matrix-multiplies and / multiplies by its inverse. If \code{e2} is an \code{sfg} object, |, /, & and %/% result in the geometric union, difference, intersection and symmetric difference respectively, and \code{==} and \code{!=} return geometric (in)equality, using \link{st_equals}.
+#' @details in case \code{e2} is numeric, +, -, *, /, %% and %/% add, subtract, multiply, divide, modulo, or integer-divide by \code{e2}. In case \code{e2} is an n x n matrix, * matrix-multiplies and / multiplies by its inverse. If \code{e2} is an \code{sfg} object, |, /, & and %/% result in the geometric union, difference, intersection and symmetric difference respectively, and \code{==} and \code{!=} return geometric (in)equality, using \link{st_equals}. If `e2` is an `sfg` or `sfc` object, for operations `+` and `-` it has to have `POINT` geometries.
 #'
 #' If \code{e1} is of class \code{sfc}, and \code{e2} is a length 2 numeric, then it is considered a two-dimensional point (and if needed repeated as such) only for operations \code{+} and \code{-}, in other cases the individual numbers are repeated; see commented examples.
 #'