# coord_proj: Similar to 'coord_map' but uses the PROJ.4 library/package... In ggalt: Extra Coordinate Systems, 'Geoms', Statistical Transformations, Scales and Fonts for 'ggplot2'

## Description

The representation of a portion of the earth, which is approximately spherical, onto a flat 2D plane requires a projection. This is what `coord_proj` does, using the `proj4::project()` function from the `proj4` package.

## Usage

 ```1 2``` ```coord_proj(proj = NULL, inverse = FALSE, degrees = TRUE, ellps.default = "sphere", xlim = NULL, ylim = NULL) ```

## Arguments

 `proj` projection definition. If left `NULL` will default to a Robinson projection `inverse` if `TRUE` inverse projection is performed (from a cartographic projection into lat/long), otherwise projects from lat/long into a cartographic projection. `degrees` if `TRUE` then the lat/long data is assumed to be in degrees, otherwise in radians `ellps.default` default ellipsoid that will be added if no datum or ellipsoid parameter is specified in proj. Older versions of PROJ.4 didn't require a datum (and used sphere by default), but 4.5.0 and higher always require a datum or an ellipsoid. Set to `NA` if no datum should be added to proj (e.g. if you specify an ellipsoid directly). `xlim` manually specify x limits (in degrees of longitude) `ylim` manually specify y limits (in degrees of latitude)

## Details

A sample of the output from `coord_proj()` using the Winkel-Tripel projection:

## Note

It is recommended that you use `geom_cartogram` with this coordinate system

When `inverse` is `FALSE` `coord_proj` makes a fairly large assumption that the coordinates being transformed are within -180:180 (longitude) and -90:90 (latitude). As such, it truncates all longitude & latitude input to fit within these ranges. More updates to this new `coord_` are planned.

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27``` ```## Not run: # World in Winkel-Tripel # U.S.A. Albers-style usa <- world[world\$region == "USA",] usa <- usa[!(usa\$subregion %in% c("Alaska", "Hawaii")),] gg <- ggplot() gg <- gg + geom_cartogram(data=usa, map=usa, aes(x=long, y=lat, map_id=region)) gg <- gg + coord_proj( paste0("+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=37.5 +lon_0=-96", " +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs")) gg # Showcase Greenland (properly) greenland <- world[world\$region == "Greenland",] gg <- ggplot() gg <- gg + geom_cartogram(data=greenland, map=greenland, aes(x=long, y=lat, map_id=region)) gg <- gg + coord_proj( paste0("+proj=stere +lat_0=90 +lat_ts=70 +lon_0=-45 +k=1 +x_0=0", " +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs")) gg ## End(Not run) ```

ggalt documentation built on May 29, 2017, 9:22 p.m.