R: Alternative to 'ggsave()', with better support for...

save_plot {cowplot}

R Documentation

Alternative to `ggsave()`, with better support for multi-figure plots.

Description

This function replaces the standard ggsave() function for saving a plot into a file. It has several advantages over ggsave(). First, it uses default sizes that work well with the cowplot theme, so that frequently a plot size does not have to be explicitly specified. Second, it acknowledges that one often first develops individual plots and then combines them into multi-plot figures, and it makes it easy—in combination with plot_grid()—to carry out this workflow. Finally, it makes it easy to adjust the aspect ratio of the figure, which is frequently necessary to accommodate plots with or without figure legend.

Usage

save_plot(
  filename,
  plot,
  ncol = 1,
  nrow = 1,
  base_height = 3.71,
  base_asp = 1.618,
  base_width = NULL,
  ...,
  cols,
  rows,
  base_aspect_ratio,
  width,
  height
)

Arguments

`filename`	Name of the plot file to generate.
`plot`	Plot to save.
`ncol`	Number of subplot columns.
`nrow`	Number of subplot rows.
`base_height`	The height (in inches) of the plot or of one sub-plot if `nrow` or `ncol` > 1. Default is 3.71.
`base_asp`	The aspect ratio (width/height) of the plot or of one sub-plot if `nrow` or `ncol` > 1. This argument is used if `base_width = NULL` or if `base_height = NULL`; if both width and height are provided then the aspect ratio is ignored. The default is 1.618 (the golden ratio), which works well for figures with a legend.
`base_width`	The width (in inches) of the plot or of one sub-plot if `nrow` or `ncol` > 1. Default is `NULL`, which means that the width is calculated from `base_height` and `base_aspect_ratio`.
`...`	Other arguments to be handed to `ggsave2()`.
`cols`	Deprecated. Use `ncol`.
`rows`	Deprecated. Use `nrow`.
`base_aspect_ratio`	Deprecated. Use `base_asp`.
`width`	Deprecated. Don't use.
`height`	Deprecated. Don't use.

Details

The key idea for this function is that plots are often grids, with sup-plots at the individual grid locations. Therefore, for this function we specify a base width and aspect ratio that apply to one sup-plot, and we then specify how many rows and columns of subplots we have. This means that if we have code that can save a single figure, it is trivial to adapt this code to save a combination of multiple comparable figures. See examples for details.

Examples


library(ggplot2)

# save a single plot with a legend
p1 <- ggplot(mpg, aes(x = cty, y = hwy, color = factor(cyl))) +
  geom_point(size = 2) +
  theme_half_open()

file1 <- tempfile("file1", fileext = ".png")
file2 <- tempfile("file2", fileext = ".png")
save_plot(file1, p1)
# same as file1 but determine base_width given base_height
save_plot(file2, p1, base_height = NULL, base_width = 6)

# save a single plot without legend, adjust aspect ratio
x <- (1:100)/10
p3 <- ggplot(data.frame(x = x, y = x*sin(x)), aes(x, y)) +
 geom_line() +
 theme_minimal_hgrid()
file3 <- tempfile("file3", fileext = ".pdf")
save_plot(file3, p3, base_asp = 1.1)

# now combine with a second plot and save
p3b <- ggplot(data.frame(x = x, y = cos(x)+x), aes(x, y)) +
 geom_line() +
 theme_minimal_hgrid()
p4 <- plot_grid(p3, p3b, labels = "AUTO")
file4 <- tempfile("file4", fileext = ".pdf")
save_plot(file4, p4, ncol = 2, base_asp = 1.1)