# Arithmetic Operators in R

The article is about making use of arithmetic operators in R Language. The usual arithmetic operations with the usual hierarchy are:

# Addition of two or more numbers and varaibles
2 + 7

## output
[1] 9

2.2 + 8.13 + 9

## output
[1] 19.33

Note that, the symbol [1] in the output indicates the element number in this output line.

Suppose, one wants to define a variable, e.g., $x=5$

R will create an object to store that value and show it when we enter that variable. The object is not displayed on the screen but stored in the active memory of R. The object will be displayed by typing the object name on the R prompt.

To define a variable, we use an assignment operator, i.e., <- (assignment operator) which plays the role of equality (=). For example,

x <- 5
x

The assignment operator (->) may also be used. However, the assignment operator (->) assignment the value from left to right. For example,

x <- 2

will assign the value 2 to variable $x$ and

x ^ 2 -> y

assigns $x^2$ to object (variable) $y$.

Note that by assigning a new value to the same variable, the old value will automatically be over-written (deleted). For example,

x <- 4
x

x <-5
x <- 2

x

Usually, spaces are not required to separate the elements of an arithmetic expression.

Note:

• If a command is not complete at the end of a line you will see a “+” sign, which means that you have to complete the command.
• Commands are separated by a semi-colon at a new line
• Comments will be lines starting with a hash mark “#”
• Text to the right of # is ignored by the interpreter.

### Use of Arithmetic Operators in R to Compute a Formula

Question: Find the distance between 2 points (2, 4, 6), and (4.2, 7.1, 8.6).

Solution: The distance between two points say $(x_1,x_2,x_3)$ and $(y_1,y_2,y_3)$ is defined as $$\sqrt{(x_1-y_1)^2 + (x_2-y_2)^2 + (x_3-y_3)^2}$$. The R code may be like:

sqrt((2-4.2)^2 + (4-7.2)^2 + (6-8.6)^2)

# alternatively one can store point values such as
x1 = 2
x2 = 4
x3 = 6
y1 = 4.2
y2 = 7.1
y3 = 8.6

sqrt((x1-y1)^2 + (x2-y2)^2 + (x3-y3)^2)

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