cowplot (version 0.5.0)

save_plot: 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 the figure legend.

Usage

save_plot(filename, plot, ncol = 1, nrow = 1, base_height = 4,
  base_aspect_ratio = 1.1, base_width = NULL, ..., cols = NULL,
  rows = NULL)

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 4.

base_aspect_ratio

The aspect ratio of the plot or of one sub-plot if nrow or ncol > 1. This argument is only used if base_width = NULL. The default is 1.1, which works well for figures without 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 height and base_aspect_ratio.

...

Other arguments to be handed to ggsave().

cols

Deprecated. Like ncol.

rows

Deprecated. Like nrow.

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

# save a single plot without legend
x <- (1:100)/10
p1 <- qplot(x, 2*x+5, geom='line')
save_plot("p1.pdf", p1)
# now combine with a second plot and save
p2B <- qplot(x, -x^2+10*x-3, geom='line')
p2 <- plot_grid(p1, p2B, labels=c("A", "B"))
save_plot("p2.pdf", p2, ncol = 2)
# save a single plot with legend, changing the aspect ratio to make room for the legend
p3 <- ggplot(mpg, aes(x = cty, y = hwy, colour = factor(cyl))) + geom_point(size=2.5)
save_plot("p3.png", p3, base_aspect_ratio = 1.3)