# star_scale: Compute regular star polygon scale or angles In gridpattern: 'grid' Pattern Grobs

## Description

`star_scale()` computes star `scale` value given an internal or external angle. `star_angle()` computes star angle (internal or external) given a `scale` value.

## Usage

 ```1 2 3``` ```star_scale(n_vertices, angle, external = FALSE) star_angle(n_vertices, scale, external = FALSE) ```

## Arguments

 `n_vertices` Number of exterior vertices. `angle` Angle in degrees. `external` If `TRUE` angle should be considered an external angle. `scale` Scale from 0 to 1.

## Details

`grid.pattern_regular_polygon()` parameterizes regular star polygons with the number of its external vertices and a `scale` that equals the fraction of the radius of the circle that circumscribes the interior vertices divided by the radius of the circle that circumscribes the exterior vertices. These helper functions help convert between that parameterization and either the internal or external angle of the regular star polygon.

## Value

`star_scale()` returns a numeric value between 0 and 1 intended for use as the `scale` argument in `grid.pattern_regular_polygon()`. `star_angle()` returns a numeric value between 0 and 360 (degrees).

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11``` ``` # |8/3| star has internal angle 45 degrees and external angle 90 degrees scale <- star_scale(8, 45) scale2 <- star_scale(8, 90, external = TRUE) all.equal(scale, scale2) star_angle(8, scale) star_angle(8, scale, external = TRUE) if (require("grid")) { grid.pattern_regular_polygon(shape = "star8", scale = scale, angle = 0, spacing = 0.2, density = 0.8) } ```

gridpattern documentation built on July 17, 2021, 9:07 a.m.