Attribute table

Converts a single or a multi-layer raster into an attribute table (data.frame).

attTbl(r, var_names = NULL)

Arguments

r

single or multi-layer raster of the class SpatRaster (see help("rast", terra)).

var_names

character vector, raster layers' names in the attribute table. If NULL, then the original layers' names are used.

Value

data.frame

Details

Attribute tables come with a column named "Cell" which stores raster cell numbers and associate each row of the attribute table with a cell of the raster object. The remaining columns of the attribute table store the data contained in the raster layers. Note that only raster cells having no missing value in no layer (complete cases) are included in the attribute table.

Note

Attribute table contains only complete cases, i.e., raster cells having a value for every layer of the stack.

Examples

library(scapesClassification)
library(terra)

## CREATE A DUMMY RASTER ##
r <- terra::rast(matrix(c(NA,100,100,NA,100,100,0,0,0),
                        nrow = 3,
                        ncol = 3,
                        byrow = TRUE))

## RASTER CELL NUMBERS ##
rcn <- r; rcn[] <- 1:9

## PLOT DATA AND CELL NUMBERS ##
oldpar <- par(mfrow = c(1,2))
m <- c(4, 1, 4, 1)

plot(r, col="grey90", colNA="red3", mar=m, asp = NA, axes=FALSE, legend=FALSE)
text(r)
lines(r)
mtext(side=3, line=0.2, adj=0, cex=1.5, font=2, "Dummy_var")
legend("bottomright", ncol=1, bg="white", fill=c("red3"),
       legend = c("NA cells (1 and 4)"))

plot(rcn, col="grey90", mar=m, asp=NA, axes=FALSE, legend=FALSE)
text(rcn)
lines(rcn)
mtext(side=3, line=0.2, adj=0, cex=1.5, font=2, "Cell numbers")

par(oldpar)

## VISUALIZE ATTRIBUTE TABLE ##

at <- attTbl(r, var_names = c("dummy_var"))
at
#>   Cell dummy_var
#> 1    2       100
#> 2    3       100
#> 3    5       100
#> 4    6       100
#> 5    7         0
#> 6    8         0
#> 7    9         0

# Note that cells 1 and 4 have missing values and therefore are not included in the table
any(at$Cell %in% c(1,4))
#> [1] FALSE