When using raster::rasterize, I can feed a polygon attribute that is character for example state names. It converts the characters to integer values. How to find out what are the corresponding character/string for each integer value?
> rfc
class : SpatialPolygonsDataFrame
features : 23
extent : -179.1332, 179.788, 13.23231, 71.39809 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=longlat +datum=NAD83 +no_defs
variables : 5
names : SITE_ID, STATE, RFC_NAME, RFC_CITY, BASIN_ID
min values : ACR, AK, Alaska, Anchorage, ABRFC
max values : TUA, UT, West Gulf, Tulsa, WGRFC
which from that
> rfc$BASIN_ID
[1] AKRFC MBRFC CBRFC ABRFC CNRFC LMRFC MARFC NCRFC NERFC NWRFC OHRFC SERFC
[13] WGRFC WGRFC WGRFC WGRFC WGRFC WGRFC WGRFC WGRFC WGRFC WGRFC WGRFC
13 Levels: ABRFC AKRFC CBRFC CNRFC LMRFC MARFC MBRFC NCRFC NERFC ... WGRFC
now if I use rasterize, it will return the following:
r
class : RasterLayer
dimensions : 3840, 4608, 17694720 (nrow, ncol, ncell)
resolution : 1000, 1000 (x, y)
extent : -2304000, 2304000, -1920001, 1919999 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=lcc +lat_1=30 +lat_2=60 +lat_0=40.0000076293945 +lon_0=-97 +x_0=0 +y_0=0 +a=6370000 +b=6370000 +units=m +no_defs
data source : in memory
names : layer
values : 1, 13 (min, max)
factors are represented internally as integers with character labels for each distinct number (level)
As such
levels(rfc$BASIN_ID)
should return a character vector of length 13, which will correspond to the numbers 1,...13 present in the rasterLayer r.