Basics of R scripts

Through this tutorial, I’m hoping to explain the basics of R scripts. Even though these will seem easy, they are essential components for almost all other activities in R.

Before starting, open R studio and open a new R script through,

File > New File> R Script

1. First script : Calculator

R can be used as a simple calculator

E.g.,

#To add two numbers 
## Input

1+1

## Output
[1] 2

2. Run your script

To obtain the output, you can type the code directly in the console and press Enter or can write the code in a R script (which is the most used method) and once you are ready to run the code, highlight the part you want to run and press Alt + Enter or Click Run on the upper right corner of the script file

3. Adding comments in script

The # in R code is used when you need to place a comment. When # is used, R ignore that particular line of code. It is possible to use multiple hash (#) symbols too!

Not a comment - not ignored by R
# A comment - Ignored by R
#### A comment - Ignored by R

4. Arithmetic operators

The following are the basic arithmetic operators used in R scripts:

Basic arithmetic operators in R

Now, let’s see how these operators are being used.

• Addition

# Addition
5 + 2
#Output
[1] 7

• Subtraction

# Subtraction
5-2
#Output
[1] 3

• Multiplication

# Multiplication
5*2
#Output
[1] 10

• Division

# Division
5/2
#Output
[1] 2.5

• Raise to power

# Raise to power
5^2
#Output
[1] 25

• Integer division

# Integer division
5%/%2
#Output
[1] 2

• Remainder of integer division

# Remainder of integer division
5%%2
#Output
[1] 1

4. Assign a variable

Assigning variables is similar to assigning roles to actors in a play. If we are playing Cinderella for example, the cast would have Cinderella, evil step-mother, evil-sisters, fairy god-mother and the prince essentially. In R, likewise if your function is the play, you allocate roles each variable has to perform. This is the key in assigning a variable.

To assign the variable ‘ <- ’ is used in R.

Now let’s consider an example.

Say you need to obtain the percent score (Percentage) for various tests. For this, you need two variables,

• Numerator being the score received for the test (Score)
• Denominator being the total score for the particular test (Total score)

The equation would be:

Since “score” and “total score” too lengthy to type in a script, we give them two new names a and b respectively.

In other words a represents the score, and b represents total score

so by assigning a value to each variable we can calculate the percent score in R easily:

## Assigning values to a and b
a <- 35
b <- 120

## Calculate percent score 

(a/b)*100

## Output
[1] 29.16667

Now if you want to change the values, you do not need to change the equation, but simply change the values assigned to a and b accordingly.

Easy!

See the following YouTube Video to understand these concepts better: