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Compute ggsave() dimensions for a fixed panel content area

Source: R/ggsave-dims.R
hv_ggsave_dims.Rd

Given a fitted ggplot, returns width and height values such that, when passed to ggplot2::ggsave(), the resulting file has a panel content area matching width / height. The "panel content area" is the rectangular bounding box of the gtable cells tagged panel, i.e., the smallest rectangle that encloses every plotting panel. Whatever grobs fall inside that rectangle (e.g., inter-panel gutters and strip rows that sit between facet rows) are counted as part of the target; everything outside it (axes, axis titles, plot title, caption, legend, plot margins, and any strips that sit above/below or beside the panel block such as facet_grid side strips) is counted as chrome.

Usage

hv_ggsave_dims(plot, width, height, units = c("in", "cm", "mm"))

Arguments

plot

A ggplot (or patchwork) object.

width

Target panel content area width, in units.

height

Target panel content area height, in units.

units

One of "in", "cm", "mm". Default "in".

Value

A named list with elements width, height, units, shaped to splat directly into ggplot2::ggsave() via do.call() (see examples).

Details

Useful for multi-panel figure sets where a constant data region is required across PDFs regardless of label length or legend placement. Always measured with a PDF sizing device, which is why units is limited to length (inches, cm, mm); DPI is irrelevant for vector output.

See also

hv_ph_location() for the slide-placement analogue used with save_ppt().

Examples

# \donttest{
p <- ggplot2::ggplot(mtcars, ggplot2::aes(hp, mpg)) +
  ggplot2::geom_point() +
  ggplot2::labs(title = "Long title that eats vertical space",
                x = "Horsepower", y = "Miles per gallon")

dims <- hv_ggsave_dims(p, width = 4, height = 3)
do.call(
  ggplot2::ggsave,
  c(list(filename = file.path(tempdir(), "fig.pdf"), plot = p), dims)
)
# }