Title: Fast Polygon to Raster Conversion
Version: 1.1.0
Description: Provides a drop-in replacement for rasterize() from the 'raster' package that takes polygon vector or data frame objects, and is much faster. There is support for the main options provided by the rasterize() function, including setting the field used and background value, and options for aggregating multi-layer rasters. Uses the scan line algorithm attributed to Wylie et al. (1967) <doi:10.1145/1465611.1465619>.
License: MIT + file LICENSE
URL: https://github.com/ecohealthalliance/fasterize
BugReports: https://github.com/ecohealthalliance/fasterize/issues
RoxygenNote: 7.3.2
Suggests: testthat, microbenchmark, knitr, rmarkdown, spelling, geos
Depends: R (≥ 3.3.0)
Imports: Rcpp, raster (≥ 2.8-3), wk
LinkingTo: Rcpp, RcppArmadillo
Encoding: UTF-8
VignetteBuilder: knitr
Language: en-US
NeedsCompilation: yes
Packaged: 2024-10-01 06:18:41 UTC; mdsumner
Author: Noam Ross ORCID iD [aut] (Original author), Michael Sumner ORCID iD [cre, ctb], Jeroen Ooms [ctb], Antoine Stevens [ctb], EcoHealth Alliance [cph], USAID PREDICT [fnd]
Maintainer: Michael Sumner <mdsumner@gmail.com>
Repository: CRAN
Date/Publication: 2024-10-01 13:30:02 UTC

fasterize: Fast Polygon to Raster Conversion

Description

Provides a drop-in replacement for rasterize() from the 'raster' package that takes polygon vector or data frame objects, and is much faster. There is support for the main options provided by the rasterize() function, including setting the field used and background value, and options for aggregating multi-layer rasters. Uses the scan line algorithm attributed to Wylie et al. (1967) doi:10.1145/1465611.1465619.

Fast polygons-to-raster conversion

Author(s)

Maintainer: Michael Sumner mdsumner@gmail.com (ORCID) [contributor]

Authors:

Other contributors:

See Also

Useful links:

Rasterize a vector or dataframe object of polygons

Description

Rasterize set of polygons

Usage

fasterize(
  sf,
  raster,
  field = NULL,
  fun = "last",
  background = NA_real_,
  by = NULL
)

Arguments

sf

a polygon vector or data frame object with a geometry column of POLYGON and/or MULTIPOLYGON (equivalent) objects.

raster

A raster object. Used as a template for the raster output. Can be created with raster::raster(). The fasterize package provides a method to create a raster object from an polygon dataset.

field

character (or numeric vector). The name of a column in sf, providing a value for each of the polygons rasterized. If NULL (default), all polygons will be given a value of 1. If a numeric vector this value will be used as the value given to the pixel. (No recycling is done).

fun

character. The name of a function by which to combine overlapping polygons. Currently takes "sum", "first", "last", "min", "max", "count", or "any". Future versions may include more functions or the ability to pass custom R/C++ functions. If you need to summarize by a different function, use ⁠by=⁠ to get a RasterBrick and then raster::stackApply() or raster::calc() to summarize.

background

numeric. Value to put in the cells that are not covered by any of the features of x. Default is NA.

by

character. The name of a column in sf by which to aggregate layers. If set, fasterize will return a RasterBrick with as many layers as unique values of the by column.

Details

This is a high-performance replacement for raster::rasterize().

The algorithm is based on the method described in course materials provided by Wayne O. Cochran. The algorithm is originally attributed to Wylie et al. (1967) doi:10.1145/1465611.1465619.

Note that original implementation worked only for sf dataframes of class "sf", but this now works for any polygon vector (sfc, wkt, wkb, geos) or dataframe with a polygon vector supported by the wk package handlers.

Value

A raster of the same size, extent, resolution and projection as the provided raster template.

References

Wylie, C., Romney, G., Evans, D., & Erdahl, A. (1967). Half-tone perspective drawings by computer. Proceedings of the November 14-16, 1967, Fall Joint Computer Conference. AFIPS '67 (Fall). doi:10.1145/1465611.1465619

Examples

library(wk)
library(fasterize)
p123 <- c(paste0("POLYGON ((-180 -20, -140 55, 10 0, -140 -60, -180 -20),", 
                 "(-150 -20, -100 -10, -110 20, -150 -20))"), 
            "POLYGON ((-10 0, 140 60, 160 0, 140 -55, -10 0))", 
            "POLYGON ((-125 0, 0 60, 40 5, 15 -45, -125 0))")
pols <- data.frame(value = seq_along(p123), geometry = wk::as_wkt(p123))
ex <- as.numeric(wk_bbox(pols))[c(1, 3, 2, 4)]
r <- raster::raster(raster::extent(ex), res = 1)
r <- fasterize(pols, r, field = "value", fun="sum")
plot(r)

raster::plot

Description

re-exported plot method from raster package to avoid failing when trying to plot raster objects without having raster loaded first.

raster::plot

Description

re-exported raster method from raster package to avoid failing when trying to plot raster objects without having raster loaded first.