Skip to contents

Count extended for working with sf objects

Source: R/count_sf_ext.R
count_sf_ext.Rd

An extended version of dplyr::count() that makes it easier to count the occurrences of features from data that intersect with features from a second sf object (set by y) or created by passing x or data to st_make_grid_ext(). Similar to count_features() and the two functions may be combined in the future.

Usage

count_sf_ext(
  data,
  x = NULL,
  y = NULL,
  join = sf::st_intersects,
  largest = TRUE,
  wt = NULL,
  sort = FALSE,
  replace_na = FALSE,
  keep_na = FALSE,
  lims = NULL,
  geometry = TRUE,
  .id = "id",
  name = NULL,
  ...
)

Arguments

data

Data to count in relationship to y

x

Optional sf object passed to st_make_grid_ext(). Defaults to NULL.

y

If NULL (default), y defaults to an sf object created by st_make_grid_ext() using x or data (if x is NULL) as the x parameter for st_make_grid_ext(). If not NULL, y must be an sf object that has a column with the same name as .id (defaults to "id").

join

geometry predicate function with the same profile as st_intersects; see details

largest

logical; if TRUE, return x features augmented with the fields of y that have the largest overlap with each of the features of x; see https://github.com/r-spatial/sf/issues/578

wt

<data-masking> Frequency weights. Can be NULL or a variable:

  • If NULL (the default), counts the number of rows in each group.

  • If a variable, computes sum(wt) for each group.

sort

If TRUE, will show the largest groups at the top.

replace_na

If TRUE, replace NA values from count with 0.

keep_na

If TRUE, filter NA values from count. Ignored if replace_na is TRUE.

lims

Optional numeric vector with minimum or both minimum and maximum count values. If provided, any values below the minimum are set to that minimum and any values above the maximum as set to the maximum. If only one value is provided, it is assumed to be a minimum limit.

geometry

If TRUE (default) return a sf object. If FALSE, return a data frame.

.id

A name to use for the cell id column. Defaults to "id".

name

The name of the new column in the output.

If omitted, it will default to n. If there's already a column called n, it will use nn. If there's a column called n and nn, it'll use nnn, and so on, adding ns until it gets a new name.

...

Arguments passed on to st_make_grid_ext

ncol,nrow

Used to set n if either are not NULL; defaults to NULL. row and id are added as columns to the grid if they are provided.

gutter

Distance in units between each column cell; gutter effectively serves as a margin as the negative buffer is applied to all cells (including those at the edges of the grid).

desc

If TRUE, reverse standard order of cell id numbering; defaults FALSE

n

If n is NULL and square is TRUE, the grid is set automatically to be 10 cells wide, Default: NULL

what

"polygons", "corners", "centers"; set to centers automatically if style is "circle", "circle_offset" but a buffer is applied to return circular polygons.

style

Style of cell to return with options including "rect", "square", "hex", "flat_top_hex", "circle", "circle_offset"

filter

If TRUE (or if trim is TRUE) filter grid geometry by x using st_filter_ext

crs

Coordinate reference system of bounding box to return; defaults to NULL which maintains the crs of the input object.

unit

Units for buffer. Supported options include "meter", "foot", "kilometer", and "mile", "nautical mile" Common abbreviations (e.g. "km" instead of "kilometer") are also supported. Distance in units is converted to units matching GDAL units for x; defaults to "meter"

cellsize

numeric of length 1 or 2 with target cellsize: for square or rectangular cells the width and height, for hexagonal cells the distance between opposite edges (edge length is cellsize/sqrt(3)). A length units object can be passed, or an area unit object with area size of the square or hexagonal cell.

trim

If TRUE, x is trimmed to y with st_trim().

Value

A sf object or a tibble (if geometry = FALSE) with a column counting occurrences of features from data.

Examples

nc <- sf::read_sf(system.file("shape/nc.shp", package = "sf"))
data <- sf::st_sample(nc, size = 75)

# Count data based on nc
count <- count_sf_ext(data = data, y = nc, .id = "FIPS")
#> Warning: attribute variables are assumed to be spatially constant throughout all geometries
plot(count[, "n"], reset = FALSE)
plot(data, col = "gray60", pch = 3, add = TRUE)


# Count data based grid created by passing nc to st_make_grid_ext
count_grid <- count_sf_ext(data = data, x = nc, .id = "FIPS")
#> Warning: attribute variables are assumed to be spatially constant throughout all geometries
plot(count_grid[, "n"], reset = FALSE)
plot(data, col = "gray60", pch = 3, add = TRUE)