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

In cowplot: Streamlined Plot Theme and Plot Annotations for 'ggplot2'

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)

cowplot documentation built on June 22, 2024, 12:27 p.m.