# polygon2spatial_polygon: Convert a Polygon to a Spatial Polygons Object In rudeboybert/SpatialEpi: Methods and Data for Spatial Epidemiology

 polygon2spatial_polygon R Documentation

## Convert a Polygon to a Spatial Polygons Object

### Description

Converts a polygon (a matrix of coordinates with NA values to separate subpolygons) into a Spatial Polygons object.

### Usage

```polygon2spatial_polygon(
poly,
coordinate.system,
area.names = NULL,
nrepeats = NULL
)
```

### Arguments

 `poly` a 2-column matrix of coordinates, where each complete subpolygon is separated by NA's `coordinate.system` the coordinate system to use `area.names` names of all areas `nrepeats` number of sub polygons for each area

### Details

Just as when plotting with the `graphics::polygon()` function, it is assumed that each subpolygon is to be closed by joining the last point to the first point. In the matrix `poly`, NA values separate complete subpolygons. In the case with an area consists of more than one separate closed polygon, `nrepeats` specifies the number of closed polygons associated with each area.

### Value

An object of class SpatialPolygons (See SpatialPolygons-class from the sp package).

Albert Y. Kim

### References

Bivand, R. S., Pebesma E. J., and Gomez-Rubio V. (2008) Applied Spatial Data Analysis with R. Springer Series in Statistics. E. J. Pebesma and R. S. Bivand. (2005) Classes and methods for spatial data in R. R News, 5, 9–13.

### Examples

```
data(scotland)

polygon <- scotland\$polygon\$polygon
coord.system <- "+proj=eqc +lat_ts=0 +lat_0=0 +lon_0=0 +x_0=0 +y_0=0 "
coord.system <- paste(coord.system, "+ellps=WGS84 +datum=WGS84 +units=m +no_defs", sep = "")
names <- scotland\$data\$county.names
nrepeats <- scotland\$polygon\$nrepeats

spatial.polygon <- polygon2spatial_polygon(polygon,coord.system,names,nrepeats)

par(mfrow=c(1,2))
# plot using polygon function
plot(polygon,type='n',xlab="Eastings (km)",ylab="Northings (km)",main="Polygon File")
polygon(polygon)

# plot as spatial polygon object
plot(spatial.polygon,axes=TRUE)
title(xlab="Eastings (km)",ylab="Northings (km)",main="Spatial Polygon")

# Note that area 23 (argyll-bute) consists of 8 separate polygons
nrepeats[23]