---
title: "geojson package classes"
author: "Scott Chamberlain and Jeroen Ooms"
date: "`r Sys.Date()`"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{geojson package classes}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r echo=FALSE}
knitr::opts_chunk$set(
  comment = "#>",
  collapse = TRUE,
  warning = FALSE,
  message = FALSE
)
```

The `geojson` package has a function to create a GeoJSON class matching all the
GeoJSON data types:

* `point()` - Point
* `multipoint()` - MultiPoint
* `linestring()` - LineString
* `multilinestring()` - MultiLineString
* `polygon()` - Polygon
* `multipolygon()` - MultiPolygon
* `feature()` - Feature
* `featurecollection()` - FeatureCollection
* `geometrycollection()` - GeometryCollection

The following are some examples of their usage.

```{r}
library("geojson")
```

## point

```{r}
(x <- point('{ "type": "Point", "coordinates": [100.0, 0.0] }'))
class(x)
attributes(x)
```

## multipoint

```{r}
multipoint('{"type": "MultiPoint", "coordinates": [ [100.0, 0.0], [101.0, 1.0] ] }')
```

## linestring

```{r}
linestring('{ "type": "LineString", "coordinates": [ [100.0, 0.0], [101.0, 1.0] ] }')
```

## multilinestring

```{r}
str <- '{ "type": "MultiLineString",
  "coordinates": [ [ [100.0, 0.0], [101.0, 1.0] ], [ [102.0, 2.0], [103.0, 3.0] ] ] }'
multilinestring(str)
```

## polygon

```{r}
str <- '{ "type": "Polygon",
 "coordinates": [
   [ [100.0, 0.0], [100.0, 1.0], [101.0, 1.0], [101.0, 0.0], [100.0, 0.0] ]
   ]
}'
polygon(str)
```

## multipolygon

```{r}
str <- '{ "type": "MultiPolygon",
  "coordinates": [
   [[[102.0, 2.0], [103.0, 2.0], [103.0, 3.0], [102.0, 3.0], [102.0, 2.0]]],
   [[[100.0, 0.0], [101.0, 0.0], [101.0, 1.0], [100.0, 1.0], [100.0, 0.0]],
   [[100.2, 0.2], [100.8, 0.2], [100.8, 0.8], [100.2, 0.8], [100.2, 0.2]]]
  ]
}'
multipolygon(str)
```

## feature

From `geopoint` class

```{r}
pt <- point('{ "type": "Point", "coordinates": [100.0, 0.0] }')
feature(pt)
```

From character string

```{r}
str <- "{ \"type\": \"Feature\", \"properties\": {}, \"geometry\": { \"type\": \"Point\", \"coordinates\": [100.0, 0.0] } }"
feature(str)
```

## featurecollection

From feature

```{r}
pt %>% feature() %>% featurecollection()
```

From string

```{r}
file <- system.file("examples", 'featurecollection1.geojson', package = "geojson")
str <- paste0(readLines(file), collapse = " ")
featurecollection(str)
```

## geometrycollection

```{r}
str <- '{
 "type": "GeometryCollection",
 "geometries": [
   {
     "type": "Point",
     "coordinates": [100.0, 0.0]
   },
   {
     "type": "LineString",
     "coordinates": [ [101.0, 0.0], [102.0, 1.0] ]
   }
  ]
}'
geometrycollection(str)
```