surveillance: discpoly – R documentation

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discpoly

Polygonal Approximation of a Disc/Circle

Description

Generates a polygon representing a disc/circle (in planar coordinates) as an object of one of three possible classes: "Polygon", "owin", or – if rgeos (or gpclib) are available – "gpc.poly".

Usage

discpoly(center, radius, npoly = 64,
         class = c("Polygon", "owin", "gpc.poly"),
         hole = FALSE)

Arguments

`center`	numeric vector of length 2 (center coordinates of the circle).
`radius`	single numeric value (radius of the circle).
`npoly`	single integer. Number of edges of the polygonal approximation.
`class`	class of the resulting polygon (partial name matching applies). For `"owin"`, this is just a wrapper around spatstat.geom's own `disc` function.
`hole`	logical. Does the resulting polygon represent a hole?

Value

A polygon of class class representing a circle/disc with npoly edges accuracy.
If class="gpc.poly" although this formal class is not currently defined (and rgeos is not available), only the pts slot of a "gpc.poly" is returned with a warning.

Author(s)

Sebastian Meyer
This function is inspired by the disc function from package spatstat.geom.

Examples

## Construct circles with increasing accuracy and of different spatial classes
disc1 <- discpoly(c(0,0), 5, npoly=4, class = "owin")
disc2 <- discpoly(c(0,0), 5, npoly=16, class = "Polygon")

## Look at the results
print(disc1)
plot(disc1, axes=TRUE, main="", border=2)

print(disc2)
lines(disc2, col=3)

if (requireNamespace("rgeos")) { # for the "gpc.poly" class definition
    disc3 <- discpoly(c(0,0), 5, npoly=64, class = "gpc.poly")
    print(disc3)
    plot(disc3, add=TRUE, poly.args=list(border=4))
}

## if one only wants to _draw_ a circle without an object behind
symbols(0, 0, circles=5, inches=FALSE, add=TRUE, fg=5)

surveillance

Temporal and Spatio-Temporal Modeling and Monitoring of Epidemic Phenomena

v1.19.1

GPL-2

Authors

Michael H<f6>hle [aut, ths] (<https://orcid.org/0000-0002-0423-6702>), Sebastian Meyer [aut, cre] (<https://orcid.org/0000-0002-1791-9449>), Michaela Paul [aut], Leonhard Held [ctb, ths], Howard Burkom [ctb], Thais Correa [ctb], Mathias Hofmann [ctb], Christian Lang [ctb], Juliane Manitz [ctb], Andrea Riebler [ctb], Daniel Saban<e9>s Bov<e9> [ctb], Ma<eb>lle Salmon [ctb], Dirk Schumacher [ctb], Stefan Steiner [ctb], Mikko Virtanen [ctb], Wei Wei [ctb], Valentin Wimmer [ctb], R Core Team [ctb] (A few code segments are modified versions of code from base R)

Initial release

2021-03-30