将 colorFactor 调色板添加到 mapview object

Question

The aim is to provide fixed colors to factor values. I struggle applying a colorFactor scale to a mapview object. However, the palette does not seem to match zcol.

I tried the following, similar to a leaflet map.

library(mapview)

colors <- colorFactor(palette = c("Red", "Green", "Blue"),
                      levels = c("Oberfranken","Mittelfranken", "Unterfranken"))

mapview(franconia, zcol = "district",col.regions=colors)

I get the following error-message:

1: In col.regions(nregions) :   Some values were outside the color
scale and will be treated as NA

Any help on that?

the following would work on leaflet, but does not make use of mapview.

franconia %>% leaflet() %>% addTiles() %>% addPolygons(fillColor = ~colors(district))

Answer 1

I couldn't figure out how to use Beni's answer to specify which colour I wanted to apply to specific features on the map.

Turns out that colorFactor returns a function. You need to supply the field you want to use to colour the features:

library('sf')
library('leaflet')
library('mapview')
# Read in shapefile and keep the first three features
ncShp <- st_read(system.file("shape/nc.shp", package="sf"))[1:3, ]
ncShp
# Simple feature collection with 3 features and 14 fields
# Geometry type: MULTIPOLYGON
# Dimension:     XY
# Bounding box:  xmin: -81.74107 ymin: 36.23388 xmax: -80.43531 ymax: 36.58965
# Geodetic CRS:  NAD27
# AREA PERIMETER CNTY_ CNTY_ID      NAME  FIPS FIPSNO CRESS_ID BIR74 SID74 NWBIR74 BIR79 SID79 NWBIR79                       geometry
# 1 0.114     1.442  1825    1825      Ashe 37009  37009        5  1091     1      10  1364     0      19 MULTIPOLYGON (((-81.47276 3...
# 2 0.061     1.231  1827    1827 Alleghany 37005  37005        3   487     0      10   542     3      12 MULTIPOLYGON (((-81.23989 3...
# 3 0.143     1.630  1828    1828     Surry 37171  37171       86  3188     5     208  3616     6     260 MULTIPOLYGON (((-80.45634 3...

cols <- c('red', 'green', 'blue')

# Colour our features sequentially based on the NAME field
ncShp$NAME
# [1] "Ashe"      "Alleghany" "Surry" 
# Ashe will be red, Alleghany will be green, Surry will be blue

colPal <- leaflet::colorFactor(palette = cols, levels = ncShp$NAME)
# Note: use levels(ncShp$NAME) if it's already a factor

# Send it to mapview
mapview::mapview(ncShp, zcol='NAME', col.regions=colPal(ncShp$NAME))

Answer 2

mapview::mapviewColors seems to do the trick:

library(mapview)

colors <- mapviewColors(x=franconia,
                        zcol = "district", 
                        colors = c("Red", "Green", "Blue"),
                        at = c("Oberfranken","Mittelfranken", "Unterfranken"))

mapview(franconia, zcol = "district",col.regions = colors)