CODEWITHSUNDEEP
runiqueraster
TWest
TWest

Reputation: 824

Extracting 'name-values' from raster instead of the 'ID levels' assigned by R

I have the following raster in R: 

> veg
class       : RasterLayer 
dimensions  : 22142, 18123, 401279466  (nrow, ncol, ncell)
resolution  : 28.5, 28.5  (x, y)
extent      : 329232, 845737.5, 8487420, 9118467  (xmin, xmax, ymin, ymax)
coord. ref. : +proj=utm +zone=20 +south +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs 
data source : C:\Users\Desktop\RO SICAR\ibge_raster 
names       : ibge_raster 
values      : 1, 39  (min, max)
attributes  :
       ID COUNT                               NM_UVEG
 from:  1   953  Contato Savana / Floresta Estacional
 to  : 39 57506 Savana Parque sem floresta-de-galeria

I am not so familiar with the raster package but I am trying to get the list of names ("NM_VEG") associated with factor levels ("ID") that R assigned to those names. I tried:

unique(values(veg))

But R returns the levels' "ID" instead of the names in "NM_UVEG":

> unique(values(veg))
 [1] NA  5  8  4 14 34  2 13 12 28 36 26 11 25 10 16 17 33 38  3
[21] 15  9 23 29 27 32 22 31 37  6 39 35  7  1 20 24 30 19 18 21

I am sure I am missing some basic commands but I can't figure it out, any ideas? Thank you in advance!

Upvotes: 1

Views: 1018

Answers (1)

Josh O'Brien
Josh O'Brien

Reputation: 162471

levels(veg)[[1]] is the incantation you're looking for.

To show that that works, here (from here) is a some appropriate reproducible data ...

library(raster)

## Example data
r <- raster(ncol=4, nrow=2)
r[] <- sample(1:4, size=ncell(r), replace=TRUE)
r <- as.factor(r)

## Add a landcover column to the Raster Attribute Table
rat <- levels(r)[[1]]
rat[["landcover"]] <- c("land","ocean/lake", "rivers","water bodies")
levels(r) <- rat

... and here is the call that will extract a data.frame that gives the attributes associated with each level:

levels(r)[[1]]
#   ID    landcover
# 1  1         land
# 2  2   ocean/lake
# 3  3       rivers
# 4  4 water bodies

Upvotes: 2

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