# Ops: S3 Ops Group Generic Functions for simple feature geometries In sf: Simple Features for R

 Ops R Documentation

## S3 Ops Group Generic Functions for simple feature geometries

### Description

S3 Ops Group Generic Functions for simple feature geometries

### Usage

```## S3 method for class 'sfg'
Ops(e1, e2)

## S3 method for class 'sfc'
Ops(e1, e2)
```

### Arguments

 `e1` object of class `sfg` or `sfc` `e2` numeric, or object of class `sfg`; in case `e1` is of class `sfc` also an object of class `sfc` is allowed

### Details

in case `e2` is numeric, +, -, *, /,

If `e1` is of class `sfc`, and `e2` is a length 2 numeric, then it is considered a two-dimensional point (and if needed repeated as such) only for operations `+` and `-`, in other cases the individual numbers are repeated; see commented examples.

### Value

object of class `sfg`

### Examples

```st_point(c(1,2,3)) + 4
st_point(c(1,2,3)) * 3 + 4
m = matrix(0, 2, 2)
diag(m) = c(1, 3)
# affine:
st_point(c(1,2)) * m + c(2,5)
# world in 0-360 range:
library(maps)
w = st_as_sf(map('world', plot = FALSE, fill = TRUE))
w2 = (st_geometry(w) + c(360,90)) %% c(360) - c(0,90)
w3 = st_wrap_dateline(st_set_crs(w2 - c(180,0), 4326)) + c(180,0)
plot(st_set_crs(w3, 4326), axes = TRUE)
(mp <- st_point(c(1,2)) + st_point(c(3,4))) # MULTIPOINT (1 2, 3 4)
mp - st_point(c(3,4)) # POINT (1 2)
opar = par(mfrow = c(2,2), mar = c(0, 0, 1, 0))
a = st_buffer(st_point(c(0,0)), 2)
b = a + c(2, 0)
p = function(m) { plot(c(a,b)); plot(eval(parse(text=m)), col=grey(.9), add = TRUE); title(m) }
lapply(c('a | b', 'a / b', 'a & b', 'a %/% b'), p)
par(opar)
sfc = st_sfc(st_point(0:1), st_point(2:3))
sfc + c(2,3) # added to EACH geometry
sfc * c(2,3) # first geometry multiplied by 2, second by 3
nc = st_transform(st_read(system.file("gpkg/nc.gpkg", package="sf")), 32119) # nc state plane, m
b = st_buffer(st_centroid(st_union(nc)), units::set_units(50, km)) # shoot a hole in nc:
plot(st_geometry(nc) / b, col = grey(.9))
```

sf documentation built on March 18, 2022, 5:22 p.m.