Drop attributes of Spat* objects containing missing values

SpatVector: drop_na() method drops geometries where any attribute specified by ... contains a missing value.
SpatRaster: drop_na() method drops cells where any layer specified by ... contains a missing value.

Usage

# S3 method for class 'SpatVector'
drop_na(data, ...)

# S3 method for class 'SpatRaster'
drop_na(data, ...)

Arguments

data: A SpatVector created with terra::vect() or a SpatRaster terra::rast().
...: <tidy-select> Attributes to inspect for missing values. If empty, all attributes are used.

Value

A Spat* object of the same class than data. See Methods.

terra equivalent

terra::trim()

Methods

Implementation of the generic tidyr::drop_na() function.

`SpatVector`

The implementation of this method is performed on a by-attribute basis, meaning that NAs are assessed on the attributes (columns) of each vector (rows). The result is a SpatVector with potentially less geometries than the input.

`SpatRaster`

Actual implementation of drop_na().SpatRaster can be understood as a masking method based on the values of the layers (see terra::mask()).

SpatRaster layers are considered as columns and SpatRaster cells as rows, so rows (cells) with any NA value on any layer would get a NA value. It is possible also to mask the cells (rows) based on the values of specific layers (columns).

drop_na() would effectively remove outer cells that are NA (see terra::trim()), so the extent of the resulting object may differ of the extent of the input (see terra::resample() for more info).

Check the Examples to have a better understanding of this method.

Feedback needed!

Visit https://github.com/dieghernan/tidyterra/issues. The implementation of this method for SpatRaster may change in the future.

Examples


library(terra)

f <- system.file("extdata/cyl.gpkg", package = "tidyterra")

v <- terra::vect(f)

# Add NAs
v <- v %>% mutate(iso2 = ifelse(cpro <= "09", NA, cpro))

# Init
plot(v, col = "red")


# Mask with lyr.1
v %>%
  drop_na(iso2) %>%
  plot(col = "red")

# SpatRaster method

# \donttest{
r <- rast(
  crs = "EPSG:3857",
  extent = c(0, 10, 0, 10),
  nlyr = 3,
  resolution = c(2.5, 2.5)
)
terra::values(r) <- seq_len(ncell(r) * nlyr(r))



# Add NAs
r[r > 13 & r < 22 | r > 31 & r < 45] <- NA

# Init
plot(r, nc = 3)


# Mask with lyr.1
r %>%
  drop_na(lyr.1) %>%
  plot(nc = 3)


# Mask with lyr.2
r %>%
  drop_na(lyr.2) %>%
  plot(nc = 3)


# Mask with lyr.3
r %>%
  drop_na(lyr.3) %>%
  plot(nc = 3)


# Auto-mask all layers
r %>%
  drop_na() %>%
  plot(nc = 3)

# }

Drop attributes of `Spat*` objects containing missing values