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Transformed XY Cartesian coordinate system

Source: R/coord_trans_xy.R
coord_trans_xy.Rd

coord_trans_xy behaves similarly to ggplot2::coord_trans() in that it occurs after statistical transformation and will affect the visual appearance of geoms. The main difference is that it takes a single transformer that is applied to the x and y axes simultaneously. Any transformers produced by ggforce::linear_trans() that have x and y arguments should work, but any other transformers produced using scales::trans_new() that take x and y arguments should also work. Axis limits will be adjusted to account for transformation unless limits are specified with xlim or ylim.

Usage

coord_trans_xy(
  trans = NULL,
  xlim = NULL,
  ylim = NULL,
  expand = FALSE,
  default = FALSE,
  clip = "on"
)

Arguments

trans

Transformer for x and y axes.

xlim, ylim

Limits for the x and y axes.

expand

If TRUE, the default, adds a small expansion factor to the limits to ensure that data and axes don't overlap. If FALSE, limits are taken exactly from the data or xlim/ylim.

default

Is this the default coordinate system? If FALSE (the default), then replacing this coordinate system with another one creates a message alerting the user that the coordinate system is being replaced. If TRUE, that warning is suppressed.

clip

Should drawing be clipped to the extent of the plot panel? A setting of "on" (the default) means yes, and a setting of "off" means no. In most cases, the default of "on" should not be changed, as setting clip = "off" can cause unexpected results. It allows drawing of data points anywhere on the plot, including in the plot margins. If limits are set via xlim and ylim and some data points fall outside those limits, then those data points may show up in places such as the axes, the legend, the plot title, or the plot margins.

Details

This coordinate system only works with geoms where all points are defined with x and y coordinates (e.g., ggplot2::geom_point(), ggplot2::geom_polygon()). This does not currently work with geoms where point coordinates are extrapolated (e.g., ggplot2::geom_rect()). Furthermore, when used with ggplot2 3.5.0 and later, some transformation edge cases may cause problems with rendering axis lines. This includes not currently support "capping" axes. I hope to support all of these geoms, edge cases, and features in the future.

Examples

# make transformer
library(ggforce)
trans <- linear_trans(shear(2, 0), rotate(-pi / 3))

# set up data to be plotted
square <- data.frame(x = c(0, 0, 4, 4), y = c(0, 1, 1, 0))
points <- data.frame(x = runif(100, 0, 4), y = runif(100, 0, 1))

# plot data normally
library(ggplot2)
ggplot(data = points, aes(x = x, y = y)) +
  geom_polygon(data = square, fill = NA, color = "black") +
  geom_point(color = "black") +
  coord_cartesian(expand = FALSE) +
  theme_classic()


# plot data with transformation
ggplot(data = points, aes(x = x, y = y)) +
  geom_polygon(data = square, fill = NA, color = "black") +
  geom_point(color = "black") +
  coord_trans_xy(trans = trans, expand = FALSE) +
  theme_classic()