Writing Data

Overview

Teaching: 10 min
Exercises: 10 min

Questions

• How can I save plots and data created in R?

Objectives

• To be able to write out plots and data from R.

Saving plots

You can save a plot from within RStudio using the ‘Export’ button in the ‘Plot’ window. This will give you the option of saving as a .pdf or as .png, .jpg or other image formats.

Sometimes you will want to save plots without creating them in the ‘Plot’ window first. Perhaps you want to make a pdf document with multiple pages: each one a different plot, for example. Or perhaps you’re looping through multiple subsets of a file, plotting data from each subset, and you want to save each plot, but obviously can’t stop the loop to click ‘Export’ for each one.

In this case you can use a more flexible approach. The function pdf creates a new pdf device. You can control the size and resolution using the arguments to this function.

pdf("Hclust_corplot_mtcars.pdf", width=5, height=5)
corrplot(cor_mtcars, order = "hclust", addrect = 3)

# You then have to make sure to turn off the pdf device!
dev.off()

Open up this document and have a look.

The commands jpeg, png etc. are used similarly to produce documents in different formats.

Writing data

At some point, you’ll also want to write out data from R.

We can use the write.table function for this, which is very similar to read.table from before.

Let’s create a data-cleaning script, for this analysis, we only want to focus on the gapminder data for Australia:

aust_subset <- gapminder[gapminder$country == "Australia",]

write.table(aust_subset,
  file="gapminder-aus.csv",
  sep=",",
  row.names = FALSE,
  quote = FALSE
)

or directly as a .csv file

aust_subset <- gapminder[gapminder$country == "Australia",]

write.csv(aust_subset,
  file="gapminder-aus.csv",
  row.names = FALSE,
  quote = FALSE
)

Key Points

• Save plots from RStudio using the ‘Export’ button.

• Use write.table to save tabular data.