Introduction to R

Using R as your calculator

sin(2*pi/3)     # <--- this symbol is for comments.

## [1] 0.8660254

5^2             # Same as 5*5.

## [1] 25

sqrt(4)         # Square root of 4.

## [1] 2

log(1)          # Natural logarithm of 1.

## [1] 0

c(1,2,3,4,5)    # Collection of the first 5 integers.

## [1] 1 2 3 4 5

c(1,2,3,4,5)*2  # First five even numbers.

## [1]  2  4  6  8 10

Assign values to variables and perform logical operation (P.97-98)

x <- 10 # x as 10
y <- 5 # y as 5
x>=y # if x is greater or equal to y

## [1] TRUE

x==y # if x is equal to y

## [1] FALSE

x!=y # if x is not equal to y

## [1] TRUE

R datatypes: can use typeof() to find the data type

# Numeric 
x <- 7.3
print(typeof(x))  # Will print "double"

## [1] "double"

# Integer
x <- 5L
print(typeof(x))  # Will print "integer"

## [1] "integer"

# Complex
x <- 3 + 2i
print(typeof(x))  # Will print "complex"

## [1] "complex"

# Logical
x <- TRUE
print(typeof(x))  # Will print "logical"

## [1] "logical"

# Character
x <- "Hello, World!"
print(typeof(x))  # Will print "character"

## [1] "character"

R also include objects including vectors, data frames etc.

# Vector
x <- c(7.3, 5.4, 9.7) #must be same data types
print(x)

## [1] 7.3 5.4 9.7

# List
x <- list("Hello", TRUE, 5L, 7.3) #can be different data types
print(x)

## [[1]]
## [1] "Hello"
## 
## [[2]]
## [1] TRUE
## 
## [[3]]
## [1] 5
## 
## [[4]]
## [1] 7.3

# Matrix
x <- matrix(1:9, nrow=3, ncol=3)
print(x)

##      [,1] [,2] [,3]
## [1,]    1    4    7
## [2,]    2    5    8
## [3,]    3    6    9

# Data frame
x <- data.frame(name=c("Alice", "Bob"), age=c(25, 31))
print(x)

##    name age
## 1 Alice  25
## 2   Bob  31

Now we are ready to generate random observations in R (P.74)

# Random floating number between 0 and 1
random_float <- runif(1)
print(random_float)

## [1] 0.5209113

# Four random observations from a Uniform [2,7]
runif(n = 4, min=2, max=7)

## [1] 2.638357 6.127518 6.612049 6.239219