SAS MBA Life/Sejong MBA2018.03.09 11:55

R - Download

https://cran.r-project.org/mirrors.html

 

R Studio

https://www.rstudio.com/products/rstudio/download/

 

Packages

  • install.packages("package_name")
  • library(package_name)

 

Loading data

  • data(dataset_name)
  • get()
  • setwd()

 

How it works

In the editor on the right you should type R code to solve the exercises. When you hit the 'Submit Answer' button, every line of code is interpreted and executed by R and you get a message whether or not your code was correct. The output of your R code is shown in the console in the lower right corner.

R makes use of the # sign to add comments, so that you and others can understand what the R code is about. Just like Twitter! Comments are not run as R code, so they will not influence your result. For example, Calculate 3 + 4 in the editor on the right is a comment.

You can also execute R commands straight in the console. This is a good way to experiment with R code, as your submission is not checked for correctness.


 

Arithmetic with R

In its most basic form, R can be used as a simple calculator. Consider the following arithmetic operators:

  • Addition: +
  • Subtraction: -
  • Multiplication: *
  • Division: /
  • Exponentiation: ^
  • Modulo: %%

The last two might need some explaining:

  • The ^ operator raises the number to its left to the power of the number to its right: for example 3^2 is 9.
  • The modulo returns the remainder of the division of the number to the left by the number on its right, for example 5 modulo 3 or 5 %% 3 is 2.

With this knowledge, follow the instructions below to complete the exercise.


 

Variable assignment

A basic concept in (statistical) programming is called a variable.

A variable allows you to store a value (e.g. 4) or an object (e.g. a function description) in R. You can then later use this variable's name to easily access the value or the object that is stored within this variable.

You can assign a value 4 to a variable my_var with the command

my_var <- 4

Variable assignment (2)

Suppose you have a fruit basket with five apples. As a data analyst in training, you want to store the number of apples in a variable with the name my_apples.

Variable assignment (3)

Every tasty fruit basket needs oranges, so you decide to add six oranges. As a data analyst, your reflex is to immediately create the variable my_oranges and assign the value 6 to it. Next, you want to calculate how many pieces of fruit you have in total. Since you have given meaningful names to these values, you can now code this in a clear way:

my_apples + my_oranges

 

Basic data types in R

R works with numerous data types. Some of the most basic types to get started are:

  • Decimals values like 4.5 are called numerics.
  • Natural numbers like 4 are called integers. Integers are also numerics.
  • Boolean values (TRUE or FALSE) are called logical.
  • Text (or string) values are called characters.

Note how the quotation marks on the right indicate that "some text" is a character.


What's that data type?

Do you remember that when you added 5 + "six", you got an error due to a mismatch in data types? You can avoid such embarrassing situations by checking the data type of a variable beforehand. You can do this with the class() function, as the code on the right shows.


 

 

 

 

 

Posted by Intoxicated BK