I'm working with shapefile in R and I need to calculate the polygons' area that I created by Gdiference function, So ,now I need to create a column with the size of freshly polygons created, because after that I need take out the small polygons which are not important to my academic research
I didn't use any function yet.
Can you provide data for an example? Anyways, try this:
library(sf)
f <- st_read("shapefile.shp")
f$area <- st_area(f) #Take care of units
Best
sp package's methods for representing spatial data in R (in this case, a SpatialPolygonsDataFrame). If you want to convert the sf polygon dataframe back to an SPDF, use as(f, 'Spatial'). To go from sp to sf, you can use sf::st_as_sf(f). If all you want to do is write your result back to disk, you don't have to convert to sp first - just use sf::st_write().
Commented
Jun 27, 2018 at 3:24
Use sf::st_area
Pro tip: dplyr::mutate allows you to do multiple computations at once. For example, if your shapefile units are in meters, you can easily compute the area in acres or hectares as well.
library(sf); library(tidyverse)
p <- st_read("polygon.shp")
p %>%
dplyr::mutate(area_meters = st_area(p),
# 1 m2 = 0.0.000247105 acres
area_acres = area_meters * 0.0.000247105,
# 1m2 = 0.0001 hectares
area_hectares = area_meters * 0.0001)
sf::st_area is a unit class object so, you can simply use units::set_units to change the unit to something else eg., set_units(st_area(p), "acre") and not have to remember conversion factors.
Commented
Nov 10, 2022 at 22:08