7

My question is about how to save a ggplot2 graph in respect with the aspect ratio. If I make a simple graphic and set the dimension of the plot with ggsave(), the plot will occupy the entire area of the saved file.

library(ggplot2)
library(sf)
#> Linking to GEOS 3.7.1, GDAL 2.4.2, PROJ 5.2.0
#> WARNING: different compile-time and runtime versions for GEOS found:
#> Linked against: 3.7.1-CAPI-1.11.1 27a5e771 compiled against: 3.7.0-CAPI-1.11.0
#> It is probably a good idea to reinstall sf, and maybe rgeos and rgdal too

df <- data.frame(
  longitude = -47,
  latitude = 45
)

p <- ggplot(df, aes(x = longitude, y = latitude)) +
  geom_point() +
  theme(
    plot.background = element_rect(fill = "black")
  )

tf <- tempfile(fileext = ".png")
ggsave(tf, p, width = 4, height = 4)

p

In the following example, I transform the data into an sf object and plot it using geom_sf() This cause the plot to have a certain aspect ratio to match the chosen projection.

df <- st_as_sf(df, coords = c("longitude", "latitude"), crs = 4326)

p <- ggplot(df) +
  geom_sf() +
  theme(
    plot.background = element_rect(fill = "black")
  )

tf <- tempfile(fileext = ".png")

However, setting the dimensions to 4 x 4 will cause paddings (white borders) to appear on the side of the plot. Hence, these white borders will be present when the graph is pasted into a PowerPoint presentation (for example).

ggsave(tf, p, width = 4, height = 4)

p

You can open tf and see the white padding around the black area. My question is about, how can I find the correct aspect ratio of the plot so I can provide appropriate dimensions to ggsave().

# Which dimensions to use to respect the aspect ratio of the map? 
# ggsave(tf, p, width = xxx, height = yyy)

Created on 2019-11-28 by the reprex package (v0.3.0)

Philippe Massicotte
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    I found this solution useful. https://community.rstudio.com/t/aspect-ratio-of-a-plot-produced-with-ggplot2-coord-quickmap/9282/2 – pasipasi Nov 28 '19 at 13:34

2 Answers2

4

Here is my solution to remove borders around ggplot2 graphs: https://www.pmassicotte.com/post/removing-borders-around-ggplot2-graphs/

Philippe Massicotte
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    Unfortunately, this link is not working for me - looks like the url changed. New link (assuming this is the same post you shared originally): https://www.pmassicotte.com/posts/2019-12-20-removing-borders-around-ggplot2-graphs/ – FishyFishies Sep 13 '22 at 13:56
3

Since I'm working in png, instead I used a hint about package magick (apologies but I've lost the link). In passing, this also adds a logo in the top left.

library(tidyverse)
library(magick)

# filename, based on subtitle in my case, but you could use title
gg_file <- paste0("graphs/", last_plot()$labels$subtitle,".png")
# save with known width and unknown height
# without an annoying message about the size used
suppressMessages(ggsave(gg_file, plot = last_plot(), 
  width = 20, units = "cm"))

# remove whitespace in this png
# and add a little back to make room for a logo
# and to stop it looking too squashed
# you did also want a logo? mine is about 100 pixels square
m_png <- image_border(image_trim(image_read(gg_file)), 
  "white", "30x30")
m_logo <- image_composite(m_png, logo %>% image_scale("120"))
image_write(m_logo, gg_file)
Scrope
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