https://stat.ethz.ch/pipermail/r-sig-geo/2025-May/029541.html
Below we calculate individual distances along polygon edges, and sum up. This works here only because this is a single-ring polygon.
The numbers in play are
129.248935: the planar distance in the crs
129.285384: the "true" distance, to some insanely accurate level
| library(tidycensus) | |
| library(tidyverse) | |
| library(sf) | |
| library(tmap) | |
| birth <- get_acs(geography = "county", year = 2023, table = "B13002", geometry = TRUE, | |
| summary_var = "B13002_001") | |
| marriage <- get_acs(geography = "county", year = 2023, table = "B12001", | |
| summary_var = "B12001_001") |
List files and stream (non-spatial) table from within a tarball on CRAN.
(we need dev gdalraster for the full dir/vsitar listing capability, but reading from remote files or archives is available in many GDAL versions and existing supported GDAL packages on CRAN)
cransrc <- "https://cran.r-project.org/src/contrib"
library(gdalraster) ## for listing dirs recursively we need gh:USDAForestService/gdalraster for now
#> GDAL 3.10.0dev-449d5f09b7, released 2024/08/26, GEOS 3.12.2, PROJ 9.4.1
## list all R packages .tar.gz
| #' Documentation of sf and tidyverse compatibility | |
| #' | |
| #' date-created: 2023-12-15 | |
| #' date-modified: 2024-10-30 | |
| # Notes to add to https://geocompr.r-universe.dev/articles/geocompkg/tidyverse-pitfalls.html | |
| library(sf) | |
| library(tidyverse) | |
| nc = st_read(system.file("shape/nc.shp", package="sf")) |
Here is some code to explore the variety available in calculating area across various packages.
x <- rnaturalearth::ne_countries(country = c("Greenland", "Spain"), returnclass = "sf")
as.numeric(sf::st_area(x))/1e6
## Greenland 2.166e6 km² -41, 72
## Spain 505990 km² -2, 40
| library("sf") | |
| file = system.file("shape/nc.shp", package = "sf") | |
| shp = read_sf(file) | |
| ## write zipped shapefile | |
| write_sf(shp, "myshapefile.shp.zip", driver = "ESRI Shapefile") | |
| ## read zipped shapefile | |
| read_sf("myshapefile.shp.zip") |
| CODE_2022,PMUN19,PMUN18,PMUN17,PMUN16,PMUN15,PMUN14,PMUN13,PMUN12,PMUN11,PMUN10,PMUN09,PMUN08,PMUN07,PMUN06,PSDC99,PSDC90,PSDC82,PSDC75,PSDC68,PSDC62,PTOT54,PTOT36,PTOT1931,PTOT1926,PTOT1921,PTOT1911,PTOT1906,PTOT1901,PTOT1896,PTOT1891,PTOT1886,PTOT1881,PTOT1876 | |
| 01001,779,771,776,767,767,767,767,777,780,784,787,791,804,811,728,579,477,368,347,407,424,506,540,543,566,560,629,637,572,594,622,605,604 | |
| 01002,256,253,248,243,241,239,236,235,234,221,207,194,195,198,168,159,136,106,88,103,157,203,219,253,256,291,323,357,391,421,486,490,484 | |
| 01004,14134,14204,14035,14081,14127,14022,14359,14233,13839,13835,13350,12792,12696,12709,11436,10455,9737,9550,8949,7748,7159,6846,6794,5705,4796,4334,4100,4023,3548,3635,3618,3396,3427 | |
| 01005,1751,1720,1689,1671,1619,1627,1635,1642,1600,1616,1592,1567,1544,1436,1408,1156,848,756,627,588,570,593,618,690,698,805,805,835,852,862,882,879,848 | |
| 01006,112,112,111,110,109,109,108,110,112,116,120,123,125,120,86,76,65,82,108,107,111,141,135,161,150,159,193,200,206,200,200,213,191 | |
| 01007,2800, |