Plot a Polygon Shaded Area

Plot a shaded area (interval) along a line via a polygon. Typically for shading a confidence interval about a line. This is just a convenient wrapper that makes more sense of the polygon() function.

Usage

plotPolygon(upper, lower, add = FALSE, col = ggplot2::alpha("blue", 0.5), ...)

addPolygon(upper, lower, col = ggplot2::alpha("blue", 0.5), ...)

Arguments

upper

A list of length 2 containing the sequential (x, y) values for the upper bound, where:

1. entry 1 contains a vector of x-values,

2. entry 2 contains a vector of y-values.

lower

A list of length 2 containing the sequential (x, y) values for the lower bound, where:

1. entry 1 contains a vector of x-values,

2. entry 2 contains a vector of y-values.

add

Logical. Should the shaded area (polygon) be added to an existing plot?

col

Color for the shaded area.

...

Additional arguments passed to the plot() function. Typically for arguments like: main, xlab, ylim, etc.

Value

A polygon plot

Functions

• addPolygon(): A convenient wrapper for adding a polygon to an existing plot which simply hard codes the add = TRUE argument and passes additional arguments to plotPolygon().

See also

polygon()

Other base R: figure()

Author

Stu Field

Examples

poly_data <- withr::with_seed(1, rnorm(1))
for ( i in 2:500 ) poly_data[i] <- poly_data[i - 1] + rnorm(1)
plotPolygon(list(1:length(poly_data), poly_data + 10),
           list(1:length(poly_data), poly_data - 10),
           xlab = "", ylab = "", main = "Polygon Wrapper")
addPolygon(list(1:length(poly_data), poly_data + 5),
           list(1:length(poly_data), poly_data - 5))
lines(poly_data, lwd = 2)


# A full test wrapper (a simulation of genetic drift)
polywrap <- function(filename = NULL, seed = 1000) {
  figure(filename, width = 960, scale = 1.1)
  on.exit(close_figure(filename))
  poly_data <- withr::with_seed(seed, rnorm(1)) # initiate random
  for ( i in 2:500 ) {
    poly_data[i] <- poly_data[i - 1] + rnorm(1)
  }
  plotPolygon(list(1:length(poly_data), poly_data + 10),
              list(1:length(poly_data), poly_data - 10),
              xlab = "", ylab = "", main = "Polygon Wrapper")
  addPolygon(list(1:length(poly_data), poly_data + 5),
             list(1:length(poly_data), poly_data - 5),
             col = ggplot2::alpha("red", 0.5))
  lines(poly_data, lwd = 2)
}

if ( interactive() ) {
  file <- tempfile("polygon-", fileext = ".png")
  polywrap(file)
}