wellknown tutorial

for v0.1.0

wellknown is an R client to convert WKT to GeoJSON, and GeoJSON to WKT. Well-known text is perhaps not as widely known as GeoJSON, but is widely used when storing geosptial data in SQL databases. Many RDBMS engines provide support. There is a binary equivalent, Well-known binary, that will hopefully come later in this package. WKT has similar spatial objects as GeoJSON, but the format is pretty different.

You can find the WKT specification in a PDF at https://portal.opengeospatial.org/files/?artifact_id=25355.

WKT from R stuctures

There’s a family of functions in wellknown that make it easy to go from familiar R objects like lists and data.frames to WKT, including:

point() - make a point, e.g., POINT (-116 45)
multipoint() - make a multipoint, e.g., MULTIPOINT ((100 3), (101 2))
linestring() - make a linestring, e.g., LINESTRING (100 0, 101 1)
polygon() - make a polygon, e.g., POLYGON ((100 0), (101 0), (101 1), (100 0))
multipolygon() - make a multipolygon, e.g., MULTIPOLYGON (((30 20, 45 40, 10 40, 30 20)), ((15 5, 40 10, 10 20, 5 10, 15 5)))

The above currently accept (depending on the fxn) numeric, list, and data.frame (and character for special case of EMPTY WKT objects).

Geojson to WKT and vice versa

geojson2wkt() and wkt2geojson() cover a subset of the various formats available:

Point
MultiPoint
Polygon
MultiPolygon
LineString
MultilineString
Geometrycollection

Geojson to WKT

geojson2wkt() converts any geojson as a list to a WKT string (the same format )

WKT to Geojson

wkt2geojson() converts any WKT string into geojson as a list. This list format for geojson can be used downstream e.g., in the leaflet package.

## Installation Stable version from CRAN ```r install.packages("wellknown") ``` Development version from GitHub ```r devtools::install_github("ropensci/wellknown") ``` ```r library("wellknown") ```

## Usage ### GeoJSON to WKT #### Point ```r point <- list('type' = 'Point', 'coordinates' = c(116.4, 45.2, 11.1)) geojson2wkt(point) #> [1] "POINT (116.4000000000000057 45.2000000000000028 11.0999999999999996)" ``` #### Multipoint ```r mp <- list(type = 'MultiPoint', coordinates = list( c(100.0, 3.101), c(101.0, 2.1), c(3.14, 2.18) )) geojson2wkt(mp) #> [1] "MULTIPOINT ((100.0000000000000000 3.1010000000000000), (101.0000000000000000 2.1000000000000001), (3.1400000000000001 2.1800000000000002))" ``` #### LineString ```r st <- list(type = 'LineString', coordinates = list(c(0.0, 0.0, 10.0), c(2.0, 1.0, 20.0), c(4.0, 2.0, 30.0), c(5.0, 4.0, 40.0))) geojson2wkt(st, fmt = 0) #> [1] "LINESTRING (0 0 10, 2 1 20, 4 2 30, 5 4 40)" ``` #### Multilinestring ```r multist <- list(type = 'MultiLineString', coordinates = list( list(c(0.0, -1.0), c(-2.0, -3.0), c(-4.0, -5.0)), list(c(1.66, -31023.5), c(10000.9999, 3.0), c(100.9, 1.1), c(0.0, 0.0)) )) geojson2wkt(multist) #> [1] "MULTILINESTRING ((0.0000000000000000 -1.0000000000000000, -2.0000000000000000 -3.0000000000000000, -4.0000000000000000 -5.0000000000000000), (1.6599999999999999 -31023.5000000000000000, 10000.9999000000007072 3.0000000000000000, 100.9000000000000057 1.1000000000000001, 0.0000000000000000 0.0000000000000000))" ``` #### Polygon ```r poly <- list(type = 'Polygon', coordinates = list( list(c(100.001, 0.001), c(101.12345, 0.001), c(101.001, 1.001), c(100.001, 0.001)), list(c(100.201, 0.201), c(100.801, 0.201), c(100.801, 0.801), c(100.201, 0.201)) )) geojson2wkt(poly) #> [1] "POLYGON ((100.0010000000000048 0.0010000000000000, 101.1234500000000054 0.0010000000000000, 101.0010000000000048 1.0009999999999999, 100.0010000000000048 0.0010000000000000), (100.2009999999999934 0.2010000000000000, 100.8010000000000019 0.2010000000000000, 100.8010000000000019 0.8010000000000000, 100.2009999999999934 0.2010000000000000))" ``` #### Multipolygon ```r mpoly <- list(type = "MultiPolygon", coordinates = list(list(list(c(30, 20), c(45, 40), c(10, 40), c(30, 20))), list(list(c(15, 5), c(40, 10), c(10, 20), c(5 ,10), c(15, 5)))) ) geojson2wkt(mpoly, fmt = 1) #> [1] "MULTIPOLYGON (((30.0 20.0, 45.0 40.0, 10.0 40.0, 30.0 20.0)), ((15.0 5.0, 40.0 10.0, 10.0 20.0, 5.0 10.0, 15.0 5.0)))" ``` #### GeometryCollection ```r gmcoll <- list(type = 'GeometryCollection', geometries = list( list(type = "Point", coordinates = list(0.0, 1.0)), list(type = 'LineString', coordinates = list(c(-100.0, 0.0), c(-101.0, -1.0))), list(type = 'MultiPoint', 'coordinates' = list(c(100.0, 3.101), c(101.0, 2.1), c(3.14, 2.18))) ) ) geojson2wkt(gmcoll, fmt = 0) #> [1] "GEOMETRYCOLLECTION (POINT (0 1), LINESTRING (-100 0, -101 -1), MULTIPOINT ((100.000 3.101), (101.0 2.1), (3.14 2.18)))" ``` #### Convert json or character objects You can convert directly from an object of class `json`, which is output from `jsonlite::toJSON()`. ```r library("jsonlite") (json <- toJSON(list(type = "Point", coordinates = c(-105, 39)))) #> {"type":["Point"],"coordinates":[-105,39]} ``` ```r geojson2wkt(json) #> [1] "POINT (-105 39)" ``` And you can convert from a geojson character string: ```r str <- '{"type":["LineString"],"coordinates":[[0,0,10],[2,1,20],[4,2,30],[5,4,40]]}' geojson2wkt(str) #> [1] "LINESTRING (0 0 10, 2 1 20, 4 2 30, 5 4 40)" ``` ### WKT to GeoJSON #### Point As a `Feature` ```r str <- "POINT (-116.4000000000000057 45.2000000000000028)" wkt2geojson(str) #> $type #> [1] "Feature" #> #> $geometry #> $geometry$type #> [1] "Point" #> #> $geometry$coordinates #> [1] "-116.4000000000000057" "45.2000000000000028" #> ... ``` Not `Feature` ```r wkt2geojson(str, feature = FALSE) #> $type #> [1] "Point" #> #> $coordinates #> [1] "-116.4000000000000057" "45.2000000000000028" #> #> attr(,"class") #> [1] "geojson" ``` #### Multipoint ```r str <- 'MULTIPOINT ((100.000 3.101), (101.000 2.100), (3.140 2.180))' wkt2geojson(str, feature = FALSE) #> $type #> [1] "MultiPoint" #> #> $coordinates #> $coordinates[[1]] #> [1] "100.0000000000000000" "3.1010000000000000" #> #> $coordinates[[2]] #> [1] "101.0000000000000000" "2.1000000000000001" #> ... ``` #### Polygon ```r str <- "POLYGON ((100 0.1, 101.1 0.3, 101 0.5, 100 0.1), (103.2 0.2, 104.8 0.2, 100.8 0.8, 103.2 0.2))" wkt2geojson(str, feature = FALSE) #> $type #> [1] "Polygon" #> #> $coordinates #> $coordinates[[1]] #> $coordinates[[1]][[1]] #> [1] "100.0000000000000000" "0.1000000000000000" #> #> $coordinates[[1]][[2]] #> [1] "101.0999999999999943" "0.3000000000000000" ... ``` #### MultiPolygon ```r str <- "MULTIPOLYGON (((40 40, 20 45, 45 30, 40 40)), ((20 35, 45 20, 30 5, 10 10, 10 30, 20 35), (30 20, 20 25, 20 15, 30 20)))" wkt2geojson(str, feature = FALSE) #> $type #> [1] "MultiPolygon" #> #> $coordinates #> $coordinates[[1]] #> $coordinates[[1]][[1]] #> $coordinates[[1]][[1]][[1]] #> [1] "40.0000000000000000" "40.0000000000000000" #> #> $coordinates[[1]][[1]][[2]] ... ``` #### Linestring ```r wkt2geojson("LINESTRING (0 -1, -2 -3, -4 5)", feature = FALSE) #> $type #> [1] "LineString" #> #> $coordinates #> $coordinates[[1]] #> [1] "0.0000000000000000" "-1.0000000000000000" #> #> $coordinates[[2]] #> [1] "-2.0000000000000000" "-3.0000000000000000" #> ... ``` ### lint WKT The `lint()` function uses native R to check for correct stucture of WKT strings. That is, it works, but may be slow-ish for very large strings. ```r lint("POINT (1 2)") #> [1] TRUE lint("LINESTRING EMPTY") #> [1] TRUE lint("MULTIPOINT ((1 2), (3 4), (-10 100))") #> [1] TRUE lint("POLYGON((20.3 28.6, 20.3 19.6, 8.5 19.6, 8.5 28.6, 20.3 28.6))") #> [1] TRUE lint("MULTIPOLYGON (((30 20, 45 40, 10 40, 30 20)), ((15 5, 40 10, 10 20, 5 10, 15 5)))") #> [1] TRUE lint("POINT (1 2 3 4 5)") #> [1] FALSE lint("LINESTRING (100)") #> [1] FALSE lint("MULTIPOLYGON (((30 20, 45 40, 10 40, 30 20)), ((15 5, a b, 10 20, 5 10, 15 5)))") #> [1] FALSE ```

## Citing To cite `wellknown` in publications use:
> Scott Chamberlain (2015). wellknown: Convert Between 'WKT' to 'GeoJSON'. R package version 0.1.0. https://github.com/ropensci/wellknown

## License and bugs * License: [MIT](http://opensource.org/licenses/MIT) * Report bugs at [our Github repo for wellknown](https://github.com/ropensci/wellknown/issues?state=open) [Back to top](#top)