# aggregate.sf: aggregate an 'sf' object In sf: Simple Features for R

 aggregate.sf R Documentation

## aggregate an `sf` object

### Description

aggregate an `sf` object, possibly union-ing geometries

### Usage

```## S3 method for class 'sf'
aggregate(
x,
by,
FUN,
...,
do_union = TRUE,
simplify = TRUE,
join = st_intersects
)
```

### Arguments

 `x` object of class sf `by` either a list of grouping vectors with length equal to `nrow(x)` (see aggregate), or an object of class `sf` or `sfc` with geometries that are used to generate groupings, using the binary predicate specified by the argument `join` `FUN` function passed on to aggregate, in case `ids` was specified and attributes need to be grouped `...` arguments passed on to `FUN` `do_union` logical; should grouped geometries be unioned using st_union? See details. `simplify` logical; see aggregate `join` logical spatial predicate function to use if `by` is a simple features object or geometry; see st_join

### Details

In case `do_union` is `FALSE`, `aggregate` will simply combine geometries using c.sfg. When polygons sharing a boundary are combined, this leads to geometries that are invalid; see https://github.com/r-spatial/sf/issues/681.

### Value

an `sf` object with aggregated attributes and geometries; additional grouping variables having the names of `names(ids)` or are named `Group.i` for `ids[[i]]`; see aggregate.

### Note

Does not work using the formula notation involving `~` defined in aggregate.

### Examples

```m1 = cbind(c(0, 0, 1, 0), c(0, 1, 1, 0))
m2 = cbind(c(0, 1, 1, 0), c(0, 0, 1, 0))
pol = st_sfc(st_polygon(list(m1)), st_polygon(list(m2)))
set.seed(1985)
d = data.frame(matrix(runif(15), ncol = 3))
p = st_as_sf(x = d, coords = 1:2)
plot(pol)
(p_ag1 = aggregate(p, pol, mean))
plot(p_ag1) # geometry same as pol
# works when x overlaps multiple objects in 'by':
p_buff = st_buffer(p, 0.2)
(p_ag2 = aggregate(p_buff, pol, mean)) # increased mean of second
# with non-matching features
m3 = cbind(c(0, 0, -0.1, 0), c(0, 0.1, 0.1, 0))
pol = st_sfc(st_polygon(list(m3)), st_polygon(list(m1)), st_polygon(list(m2)))
(p_ag3 = aggregate(p, pol, mean))
plot(p_ag3)
# In case we need to pass an argument to the join function:
(p_ag4 = aggregate(p, pol, mean,
join = function(x, y) st_is_within_distance(x, y, dist = 0.3)))
```

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