R: Draw polygons with expansion/contraction and/or rounded...

geom_shape {ggforce} | R Documentation

## Draw polygons with expansion/contraction and/or rounded corners

### Description

This geom is a cousin of `ggplot2::geom_polygon()` with the added possibility of expanding or contracting the polygon by an absolute amount (e.g. 1 cm). Furthermore, it is possible to round the corners of the polygon, again by an absolute amount. The resulting geom reacts to resizing of the plot, so the expansion/contraction and corner radius will not get distorted. If no expansion/contraction or corner radius is specified, the geom falls back to `geom_polygon` so there is no performance penality in using this instead of `geom_polygon`.

### Usage

    geom_shape(
      mapping = NULL,
      data = NULL,
      stat = "identity",
      position = "identity",
      expand = 0,
      radius = 0,
      ...,
      na.rm = FALSE,
      show.legend = NA,
      inherit.aes = TRUE
    )

### Arguments

`mapping` | Set of aesthetic mappings created by `aes()` or `aes_()`. If specified and `inherit.aes = TRUE` (the default), it is combined with the default mapping at the top level of the plot. You must supply `mapping` if there is no plot mapping.
`data` | The data to be displayed in this layer. There are three options: If `NULL`, the default, the data is inherited from the plot data as specified in the call to `ggplot()`. A `data.frame`, or other object, will override the plot data. All objects will be fortified to produce a data frame. See `fortify()` for which variables will be created. A `function` will be called with a single argument, the plot data. The return value must be a `data.frame`, and will be used as the layer data. A `function` can be created from a `formula` (e.g. `~ head(.x, 10)`).
`stat` | The statistical transformation to use on the data for this layer, as a string.
`position` | Position adjustment, either as a string, or the result of a call to a position adjustment function.
`expand` | A numeric or unit vector of length one, specifying the expansion amount. Negative values will result in contraction instead. If the value is given as a numeric it will be understood as a proportion of the plot area width.
`radius` | As `expand` but specifying the corner radius.
`...` | Other arguments passed on to `layer()`. These are often aesthetics, used to set an aesthetic to a fixed value, like `colour = "red"` or `size = 3`. They may also be parameters to the paired geom/stat.
`na.rm` | If `FALSE`, the default, missing values are removed with a warning. If `TRUE`, missing values are silently removed.
`show.legend` | logical. Should this layer be included in the legends? `NA`, the default, includes if any aesthetics are mapped. `FALSE` never includes, and `TRUE` always includes. It can also be a named logical vector to finely select the aesthetics to display.
`inherit.aes` | If `FALSE`, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. `borders()`.

### Aesthetics

geom_shape understand the following aesthetics (required aesthetics are in bold):

- x

- y

- color

- fill

- group

- size

- linetype

- alpha

### Note

Some settings can result in the dissappearance of polygons, specifically when contracting or rounding corners with a relatively large amount. Also note that x and y scale limits does not take expansion into account and the resulting polygon might thus not fit into the plot.

### Author(s)

Thomas Lin Pedersen

### Examples

    shape <- data.frame(
      x = c(0.5, 1, 0.75, 0.25, 0),
      y = c(0, 0.5, 1, 0.75, 0.25)
    )
    # Expand and round
    ggplot(shape, aes(x = x, y = y)) +
      geom_shape(expand = unit(1, 'cm'), radius = unit(0.5, 'cm')) +
      geom_polygon(fill = 'red')

    # Contract
    ggplot(shape, aes(x = x, y = y)) +
      geom_polygon(fill = 'red') +
      geom_shape(expand = unit(-1, 'cm'))

    # Only round corners
    ggplot(shape, aes(x = x, y = y)) +
      geom_polygon(fill = 'red') +
      geom_shape(radius = unit(1, 'cm'))

[Package ggforce version 0.3.2 Index]