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  3. Introduction to Importing Data in R

Exercise

fread: more advanced use

Now that you know the basics about fread(), you should know about two arguments of the function: drop and select, to drop or select variables of interest.

Suppose you have a dataset that contains 5 variables and you want to keep the first and fifth variable, named "a" and "e". The following options will all do the trick:

fread("path/to/file.txt", drop = 2:4)
fread("path/to/file.txt", select = c(1, 5))
fread("path/to/file.txt", drop = c("b", "c", "d"))
fread("path/to/file.txt", select = c("a", "e"))

Let's stick with potatoes since we're particularly fond of them here at DataCamp. The data is again available in the file potatoes.csv (view), containing comma-separated records.

Instructions

100 XP
  • Using fread() and select or drop as arguments, only import the texture and moistness columns of the flat file. They correspond to the columns 6 and 8 in "potatoes.csv". Store the result in a variable potatoes.
  • plot() 2 columns of the potatoes data frame: texture on the x-axis, moistness on the y-axis. Use the dollar sign notation twice. Feel free to name your axes and plot.