Exercises - First Steps

Basics of R for Data Science

Getting started and creating objects

• Open RStudio

• Create an object with a name allowed in R and assign it a numerical value

• Create a second object with a different, allowed name, and use it to store the value of the first object squared (i.e., raised to the 2^nd power)

• Try to create another object with a non-allowed name and see what happens

• Now create an object and assign it a string (character) value, then use the appropriate function to inspect the type of the object and make sure that it is character

Use basic operations

• Compute the following operations:

  • \(\frac{9}{11} + 10\)
  • \(\sqrt{941}\)
  • \(\frac{\sqrt{2 \times 5}\ + 6}{4}\)
  • \(\log_{2} 50\)

• Round each of the previous results to the third digit, using the appropriate function for rounding

• Use the appropriate relational operator to determine whether each of the previous results is greater than \(10\)

• Use the appropriate relational operator to determine whether \(3^2 + 4^2\) is equal to \(5^2\) (BTW, if this is true, then \(3, 4, 5\) is a Pythagorean triple)

Use functions

• Open the help/documentation for the Sys.time() function, then use it to determine the current (system) time and see that it is correct

• Open the help/documentation for the rep() function and understand what it does, also have a look at the Examples section in the documentation

• Generate 10 numbers randomly drawn from a standard normal distribution using the rnorm() function, save them in an object named X1

• Use the rep() function to replicate the whole X1 vector three times, and store the result in a newly created object named X2

• Use the rep() function to replicate each value of X1 thrice, and store the result in a newly created object named X3

• Be proud: the last few steps are actually the starting point for future data simulation 😀

Import/export, and more

• Use the appropriate function to know the current working directory

• Use both the the appropriate panel in RStudio and the ls() function to see all objects currently existing in the workspace (there should be all those from the previous points)

• Export the whole workspace with file name "myWSpace.RData", then close RStudio

• Re-open Rstudio, make sure that the workspace is empty after the re-opening (otherwise use rm(list=ls())), then re-import the whole workspace named "myWSpace.RData" that you had previously saved, and make sure that all objects are there

• Download this dataset, then import it in RStudio using an appropriate function, and display it in your console

• Let’s try to create and export a figure following a few steps:

  • create an object named x that includes 10 random numbers generated using rnorm();
  • create another object named y that includes other 10 random numbers generated using rnorm();
  • use the base plot() function for creating a scatter plot (i.e., plot(x, y));
  • now use the pdf() function for exporting the above scatter plot in a .pdf file.