[3] Data Types

Number

sample code(s)

x <- 1 y <- 2 x + y

[1] 3

---

Vector
(1-dimension)

sample code(s)

v1 <- c(2,4,6) v1

[1] 2 4 6

sample code(s)

v1[3]

[1] 6

sample code(s)

v2 <- c("a","b","c") v2

[1] "a" "b" "c"

sample code(s)

v2[3]

[1] "c"

sample code(s)

# One vector cannot contain both numbers and characters. When they're mixed, then all is regarded as characters. v3 <- c(1,"b","c") v3

[1] "1" "b" "c"

sample code(s)

v3[1]

[1] "1"

sample code(s)

v3[3]

[1] "c"

---

Matrix
(2-dimension)

sample code(s)

# default: column 1 first matCol1 <- matrix(c(1, 2, 3, 4, 5, 6), nrow = 2, ncol = 3) matCol1

[,1] [,2] [,3] [1,]    1    3    5 [2,]    2    4    6

sample code(s)

# byrow = TRUE: row 1 first matRow1 <- matrix(c(1, 2, 3, 4, 5, 6), nrow = 2, ncol = 3, byrow = TRUE) matRow1

[,1] [,2] [,3] [1,]    1    2    3 [2,]    4    5    6

---

Data Frame
(2-dimension; mixed structure of numbers and characters)

sample code(s)

df <- data.frame(symbol = c("AAPL", "GOOG", "GS"), action = c("Buy", "Buy", "Sell"), price = c(127.17, 532.33, 213.06), shares = c(500,100,500)) df

symbol action  price shares 1   AAPL    Buy 127.17    500 2   GOOG    Buy 532.33    100 3     GS   Sell 213.06    500

sample code(s)

df[2,3]

[1] 532.33

---

List
("A matrix which can contain any form of data like number, vector, matrix, and even a data frame.")

sample code(s)

l <- list(a = c(1, 2), b = matrix(1:6, nrow = 2, ncol = 3), c = data.frame(symbol = c("AAPL", "GOOG", "GS"), action = c("Buy", "Buy", "Sell"), price = c(127.17, 532.33, 213.06), shares = c(500,100,500))) l

$a [1] 1 2 $b      [,1] [,2] [,3] [1,]    1    3    5 [2,]    2    4    6 $c   symbol action  price shares 1   AAPL    Buy 127.17    500 2   GOOG    Buy 532.33    100 3     GS   Sell 213.06    500

sample code(s)

# The same result above. l2 <- list(a = c(1, 2), b = matrix(1:6, nrow = 2, ncol = 3), c = df) l2