Generates a 2D matrix of graduated colours by interpolating between the given colours specifying the four corners.

`colour_mat(cols, n = c(10, 10), rotate, plot = FALSE)`

- cols
vector of length >= 4 of colors (example, default =

`rainbow (4)`

, or`RColorBrewer::brewer.pal (4, 'Set1')`

).`cols`

are wrapped clockwise around the corners from top left to bottom left.- n
number of rows and columns of colour matrix (default = 10; if length 2, then dimensions of rectangle).

- rotate
rotates the entire colour matrix by the specified angle (in degrees).

- plot
plots the colour matrix.

`Matrix`

of colours.

```
cm <- colour_mat (n = 5, cols = rainbow(4), rotate = 90, plot = TRUE)
# 'colour_mat' is intended primarily for use in colouring groups added with
# 'add_osm_groups' using the 'colmat = TRUE' option:
bbox <- get_bbox (c (-0.13, 51.5, -0.11, 51.52))
# 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 <- osm_basemap (bbox = bbox, bg = "gray20")
map <- add_osm_groups (map, obj = london$dat_BNR, group = groups,
cols = rainbow (4), colmat = TRUE, rotate = 90)
print_osm_map (map)
```