Basic command and data types

Variable

Variables are objects in R use to store values. It can be single value, basic or complex arithmetic operations, or a data matrix or a data frame. Variable can be assign using either the “<-” or “=” operators. (alt+ -)

a = 5
b <- 8*3
c = "Data analysis with R"
a + b

[1] 29

c

[1] "Data analysis with R"

cat(a,c)

5 Data analysis with R

Basic command

x <-  3
y <-  2

x+y

[1] 5

class(x)

[1] "numeric"

class(y)

[1] "numeric"

x <- as.integer(x)
class(x)

[1] "integer"

sqrt(3 * 4 + 2 * 5 + 3)

[1] 5

log(5) + log(10)

[1] 3.912023

log(50) 

[1] 3.912023

sum(3 * 4 + 2 * 5 + 3)

[1] 25

Data Type

Variables can contain values of specific types within R. The six data types that R uses include:

• "numeric" —> any numerical value, including whole numbers and decimals.

• "character" —> text values, denoted by using quotes (““) around text.

• "integer" —> whole numbers (e.g., 2L, the L indicates to R that it’s an integer). It behaves similar to the numeric data type for most tasks or functions; however, it takes up less storage space than numeric data.

• "logical" —> TRUE and FALSE (the Boolean data type). The logical data type can be specified using four values, TRUE in all capital letters, FALSE in all capital letters, a single capital T or a single capital F.

Data Structure

Vector

A vector is substantially a list of variables. A vector consists of a collection of numbers, arithmetic expressions, logical values or character strings for example. However, each vector must have all components of the same type, i.e numeric, character, or logical

c(3,8,2)

[1] 3 8 2

c("mike", "John")

[1] "mike" "John"

c(5,9,"abc", TRUE)

[1] "5"    "9"    "abc"  "TRUE"

numbers <- c(38,26,35)
name <- c("mike", "john", "jane")
any_text <- c(5,9,"abc", TRUE)

class(numbers)

[1] "numeric"

class(name)

[1] "character"

class(any_text)

[1] "character"

Data Frame

Two-dimensional, tabular data structure used to store data where each column represents a variable and each row represents an observation

df <- data.frame(name, numbers)

head(df)

  name numbers
1 mike      38
2 john      26
3 jane      35

colnames(df)[2] <- "age"

names(df)[names(df)=="numbers"] <- "age"

summary(df$age)

   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
   26.0    30.5    35.0    33.0    36.5    38.0 

Matrix

A matrix in R is a collection of vectors of same length and identical datatype

data_matrix <- as.matrix(cbind(a=numbers,b=2*numbers,c=numbers/1.5))

data_matrix

      a  b        c
[1,] 38 76 25.33333
[2,] 26 52 17.33333
[3,] 35 70 23.33333