Plots spatially distinct groups of OSM objects in different colours.

## Usage

```
add_osm_groups(
map,
obj,
groups,
cols,
bg,
make_hull = FALSE,
boundary = -1,
size,
shape,
border_width = 1,
colmat,
rotate
)
```

## Arguments

- map
A

`ggplot2`

object to which the grouped objects are to be added.- obj
An

`sp`

`SpatialPointsDataFrame`

,`SpatialPolygonsDataFrame`

, or`SpatialLinesDataFrame`

(list of polygons or lines) returned by`extract_osm_objects`

.- groups
A list of spatial points objects, each of which contains the coordinates of points defining one group.

- cols
Either a vector of >= 4 colours passed to

`colour_mat`

(if`colmat = TRUE`

) to arrange as a 2-D map of visually distinct colours (default uses`rainbow`

colours), or (if`colmat = FALSE`

), a vector of the same length as groups specifying individual colours for each.- bg
If given, then any objects not within groups are coloured this colour, otherwise (if not given) they are assigned to nearest group and coloured accordingly (

`boundary`

has no effect in this latter case).- make_hull
Either a single boolean value or a vector of same length as groups specifying whether convex hulls should be constructed around all groups (

`TRUE`

), or whether the group already defines a hull (convex or otherwise;`FALSE`

).- boundary
(negative, 0, positive) values define whether the boundary of groups should (exclude, bisect, include) objects which straddle the precise boundary. (Has no effect if

`bg`

is given).- size
Size argument passed to

`ggplot2`

(polygon, path, point) functions: determines width of lines for (polygon, line), and sizes of points. Respective defaults are (0, 0.5, 0.5).- shape
Shape of points or lines (the latter passed as

`linetype`

); see`shape`

.- border_width
If given, draws convex hull borders around entire groups in same colours as groups (try values around 1-2).

- colmat
If

`TRUE`

generates colours according to`colour_mat`

, otherwise the colours of groups are specified directly by the vector of`cols`

.- rotate
Passed to

`colour_mat`

to rotate colours by the specified number of degrees clockwise.

## Note

Any group that is entirely contained within any other group is assumed to represent a hole, such that points internal to the smaller contained group are *excluded* from the group, while those outside the smaller yet inside the bigger group are included.

## Examples

```
bbox <- get_bbox (c (-0.13, 51.5, -0.11, 51.52))
# Download data using 'extract_osm_objects'
if (FALSE) {
dat_HP <- extract_osm_objects (key = 'highway',
value = 'primary',
bbox = bbox)
dat_T <- extract_osm_objects (key = 'tree', bbox = bbox)
dat_BNR <- extract_osm_objects (key = 'building', value = '!residential',
bbox = bbox)
}
# These data are also provided in
dat_HP <- london$dat_HP
dat_T <- london$dat_T
dat_BNR <- london$dat_BNR
# Define a function to easily generate a basemap
bmap <- function ()
{
map <- osm_basemap (bbox = bbox, bg = "gray20")
map <- add_osm_objects (map, dat_HP, col = "gray70", size = 1)
add_osm_objects (map, dat_T, col = "green")
}
# Highlight a single region using all objects lying partially inside the
# boundary (via the boundary = 1 argument)
pts <- sp::SpatialPoints (cbind (c (-0.115, -0.125, -0.125, -0.115),
c (51.505, 51.505, 51.515, 51.515)))
if (FALSE) {
dat_H <- extract_osm_objects (key = 'highway', bbox = bbox) # all highways
map <- bmap ()
map <- add_osm_groups (map, dat_BNR, groups = pts, cols = "gray90",
bg = "gray40", boundary = 1)
map <- add_osm_groups (map, dat_H, groups = pts, cols = "gray80",
bg = "gray30", boundary = 1)
print_osm_map (map)
}
# Generate random points to serve as group centres
set.seed (2)
ngroups <- 6
x <- bbox [1,1] + runif (ngroups) * diff (bbox [1,])
y <- bbox [2,1] + runif (ngroups) * diff (bbox [2,])
groups <- cbind (x, y)
groups <- apply (groups, 1, function (i)
sp::SpatialPoints (
matrix (i, nrow = 1, ncol = 2)))
# plot a basemap and add groups
map <- bmap ()
cols <- rainbow (length (groups))
if (FALSE) {
map <- add_osm_groups (map,
obj = london$dat_BNR,
group = groups,
cols = cols)
cols <- adjust_colours (cols, -0.2)
map <- add_osm_groups (map, obj = london$dat_H, groups = groups, cols = cols)
print_osm_map (map)
# Highlight convex hulls containing groups:
map <- bmap ()
map <- add_osm_groups (map,
obj = london$dat_BNR,
group = groups,
cols = cols,
border_width = 2)
print_osm_map (map)
}
```