dot-lwd: Line width conversion

In CMAP-REPOS/cmapplot: CMAP Themes and Color Palettes

Line width conversion

Description

The factor .lwd is used to calculate correct output sizes for line widths. For line widths in ggplot2, the size in mm must be divided by this factor for correct output. Because the user is likely to prefer other units besides for mm, gg_lwd_convert() is provided as a convenience function, converting from any unit all the way to ggplot units.

Usage

.lwd

gg_lwd_convert(value, unit = "bigpts")

Arguments

value	Numeric, the value to be converted.
unit	Char, the unit of the value to be converted. Can be any of the units accepted by grid::unit(), including "bigpts", "pt", "mm", and "in". Default is bigpts.

Format

An object of class numeric of length 1.

Details

.lwd is equal to ggplot2::.stroke / ggplot2::.pt. In ggplot2, the size in mm is divided by .lwd to achieve the correct output. In the grid package, however, the size in points (pts (or maybe bigpts? Unclear.) must be divided by .lwd. The user is unlikely to interact directly with grid, but this is how finalize_plot() does its work.

This is closely related to ggplot::.pt, which is the factor that font sizes (in pts) must be divided by for text geoms within ggplot2. Confusingly, .pt is not required for ggplot2 font sizes outside the plot area: e.g. axis titles, etc.

Functions

• gg_lwd_convert(): Function to convert from any unit directly to ggplot2's preferred millimeters.

See Also

grid's unit, ggplot2's .pt, and https://stackoverflow.com/questions/17311917/ggplot2-the-unit-of-size

Examples

ggplot() + coord_cartesian(xlim = c(-3, 3), ylim = c(-3, 3)) +

  # a green line 3 points wide
  geom_hline(yintercept = 1, color = "green", size = gg_lwd_convert(3)) +

  # black text of size 24 points
  annotate("text", -2, 0, label = "text", size = 24/ggplot2::.pt)


# a blue line 6 points wide, drawn over the plot with  the `grid` package
grid::grid.lines(y = 0.4, gp = grid::gpar(col = "blue", lwd = 6 / .lwd))

CMAP-REPOS/cmapplot documentation built on March 29, 2025, 11:55 a.m.