# geojsonio vignette

#### Scott Chamberlain

#### 2020-04-04

`geojsonio` converts geographic data to geojson and topojson formats. Nothing else. We hope to do this one job very well, and handle all reasonable use cases.

Functions in this package are organized first around what you’re working with or want to get, geojson or topojson, then convert to or read from various formats:

- `geojson_list()`/`topojson_list()` - convert to GeoJSON/TopoJSON as R list format
- `geojson_json()`/`topojson_json()` - convert to GeoJSON/TopoJSON as JSON
- `geojson_sp()` - convert output of `geojson_list()` or `geojson_json()` to spatial objects
- `geojson_read()`/`topojson_read()` - read a GeoJSON/TopoJSON file from file path or URL
- `geojson_write()`/`topojson_write()` - write a GeoJSON/TopoJSON file locally

Each of the above functions have methods for various objects/classes, including `numeric`, `data.frame`, `list`, `SpatialPolygons`, `SpatialLines`, `SpatialPoints`, etc.

Additional functions:

- `map_gist()` - push up a geojson or topojson file as a GitHub gist (renders as an interactive map) - See the maps with geojsonio vignette.
- `map_leaf()` - create a local interactive map with the `leaflet` package - See the maps with geojsonio vignette.

## Install

Install rgdal - in case you can’t get it installed from binary , here’s what works on a Mac (change to the version of `rgdal` and `GDAL` you have).

    install.packages("http://cran.r-project.org/src/contrib/rgdal_1.1-3.tar.gz", repos = NULL, type="source", configure.args = "--with-gdal-config=/Library/Frameworks/GDAL.framework/Versions/1.11/unix/bin/gdal-config --with-proj-include=/Library/Frameworks/PROJ.framework/unix/include --with-proj-lib=/Library/Frameworks/PROJ.framework/unix/lib")

Stable version from CRAN

    install.packages("geojsonio")

Development version from GitHub

    devtools::install_github("ropensci/geojsonio")

    library("geojsonio")

## GeoJSON

### Convert various formats to geojson

From a `numeric` vector of length 2

as json

    geojson_json(c(32.45, -99.74))

as a list

    geojson_list(c(32.45, -99.74))

From a `data.frame`

as json

    library('maps')
    data(us.cities)
    geojson_json(us.cities[1:2, ], lat = 'lat', lon = 'long')

as a list

    geojson_list(us.cities[1:2, ], lat = 'lat', lon = 'long')

From `SpatialPolygons` class

    library('sp')
    poly1 <- Polygons(list(Polygon(cbind(c(-100,-90,-85,-100),
      c(40,50,45,40)))), "1")
    poly2 <- Polygons(list(Polygon(cbind(c(-90,-80,-75,-90),
      c(30,40,35,30)))), "2")
    sp_poly <- SpatialPolygons(list(poly1, poly2), 1:2)

to json

    geojson_json(sp_poly)

to a list

    geojson_list(sp_poly)

From `SpatialPoints` class

    x <- c(1, 2, 3, 4, 5)
    y <- c(3, 2, 5, 1, 4)
    s <- SpatialPoints(cbind(x, y))

to json

    geojson_json(s)

to a list

    geojson_list(s)

### Write geojson

    library('maps')
    data(us.cities)
    geojson_write(us.cities[1:2, ], lat = 'lat', lon = 'long')

### Read geojson

    library("sp")
    file <- system.file("examples", "california.geojson", package = "geojsonio")
    out <- geojson_read(file, what = "sp")
    plot(out)

## Topojson

To JSON

    topojson_json(c(-99.74,32.45))

To a list

    library(sp)
    x <- c(1,2,3,4,5)
    y <- c(3,2,5,1,4)
    s <- SpatialPoints(cbind(x,y))
    topojson_list(s)

Read from a file

    file <- system.file("examples", "us_states.topojson", package = "geojsonio")
    out <- topojson_read(file, verbose = FALSE)
    summary(out)

Read from a URL

    url <- "https://raw.githubusercontent.com/shawnbot/d3-cartogram/master/data/us-states.topojson"
    out <- topojson_read(url, verbose = FALSE)

Or use `as.location()` first

    (loc <- as.location(file))
    out <- topojson_read(loc, verbose = FALSE)