Data Output

While its nice to be able to read in a variety of data formats, it’s equally important to be able to output data somewhere.

The readr package in the tidyverse provides data exporting functions which have the pattern write_*:

  • write_csv(),
  • write_delim(), others.

From write_csv() documentation:

write_csv(x, file, 
  na = "NA", append = FALSE, 
  col_names = !append, quote_escape = "double",
  eol = "\n", path = deprecated()
)

Data Output

x: data frame you want to write

file: file path where you want to R object written; it can be:

  • an absolute path,
  • a relative path (relative to your working directory),
  • a file name only (which writes the file to your working directory)
  • remember to include the file extension (.csv, .txt, or .tsv)
# Examples

write_csv(dat, file = "YouthTobacco_newNames.csv")

write_delim(dat, file = "YouthTobacco_newNames.csv", delim = ",")

GUT CHECK!

What does write_csv() do? Saves data to:

A. R’s memory

B. A file on your hard drive

C. A ggplot

R binary file

.rds is an extension for R native file format.

write_rds() and read_rds() from readr package can be used to write/read a single R object to/from file.

Saving datasets in .rds format can save time if you have to read it back in later.

# write an object: a data frame "dat"
write_rds(dat, file = "yts_dataset.rds")

# write an object: vector "x"
x <- c(1, 3, 3)
write_rds(x, file = "my_vector.rds")

# read an object from file and assign to a new object named "y"
x2 <- read_rds(file = "my_vector.rds")
x2
[1] 1 3 3

Saving multiple objects

You may want to export a set of objects from R for later use, either to save time or to use in another R script. You can output these to an .RData file individually, or save your entire Environment with save.image().

save(x, x2, file = "x_x2_output.RData")
save.image(file = "my_environment.RData")

Using RStudio for importing/exporting data

If there is an .rds or .RData file that you want to work with, you can open it into your environment using the file icon.

Can also save your entire environment or a subset of objects in your environment to a new .RData file with the save icon. Click the “List” button and switch to “Grid” to select which objects to delete or keep before saving the Environment.

REMINDER: Saving a ggplot to file

A few options:

  • RStudio > Plots > Export > Save as image / Save as PDF
  • RStudio > Plots > Zoom > [right mouse click on the plot] > Save image as
  • In the code
ggsave(filename = "saved_plot.png",  # will save in working directory
       plot = rp_fac_plot,
       width = 6, height = 3.5)               # by default in inches

Summary

  • Use write_csv() and write_delim() from the readr package to write your (modified) data
  • .rds files can be handy for saving intermediate work
  • Can save environment (or subset) using save() and save.image()

Resources & Lab