Scale polygons around their center

scale_polygon(poly, scaling)

Arguments

poly	a data frame defining a polygon (x and y coordinates)
scaling	a numeric vector that defines the scaling factor

Value

data.frame defining a scaled polygon

Examples

scale_polygon(data.frame(x = c(1, 2, 3), y = c(1, 2, 1)), 2)
#>   x         y
#> 1 0 0.6666667
#> 2 2 2.6666667
#> 3 4 0.6666667

poly <- data.frame(x = c(1, 1, 0, 0), y = c(1, 0, 0, 1))
library(ggplot2)
ggplot(data = NULL, aes(x = x, y = y)) +
  geom_polygon(data = poly, fill = "black") +
  geom_polygon(data = scale_polygon(poly, 0.5), fill = "gray") +
  geom_polygon(data = scale_polygon(poly, 2), alpha = 0.2, fill = "red") +
  geom_polygon(data = scale_polygon(poly, c(1, 3)), alpha = 0.2, fill = "green") +
  geom_polygon(data = scale_polygon(poly, c(3, 1)), alpha = 0.2, fill = "blue")