Basics of R (Review)

Assignment

a <- 2
b <- 3

a + b

5

Custom function

add <- function(a, b) {
    a + b
}

add(a, b)

5

Vectors

seq(1, 5)

1. 1
2. 2
3. 3
4. 4
5. 5

1:5

1. 1
2. 2
3. 3
4. 4
5. 5

c(1,2,3,4,5)

1. 1
2. 2
3. 3
4. 4
5. 5

Named vectors

c(a=1, b=2, c=3, d=4, e=5)

a

1

b

2

c

3

d

4

e

5

Lists

list(a=1, b=TRUE, c="hello")

$a

1

$b

TRUE

$c

'hello'

Data Frames

A Data Frame is a special kind of List where all elements are vectros fo the same length.

data.frame(a=1:5, b=6:10, c=rnorm(5))

A data.frame: 5 × 3

a	b	c
<int>	<int>	<dbl>
1	6	-0.2701866
2	7	0.4624501
3	8	0.1019228
4	9	-1.5094554
5	10	0.4304919

Basic Data Frame manipulation

df <- data.frame(a=1:5, b=6:10, c=rnorm(5))

df

A data.frame: 5 × 3

a	b	c
<int>	<int>	<dbl>
1	6	0.5207780
2	7	-1.5697044
3	8	0.3914048
4	9	-0.5415737
5	10	-0.9471250

Get columns

df$b

1. 6
2. 7
3. 8
4. 9
5. 10

df[['b']]

1. 6
2. 7
3. 8
4. 9
5. 10

df[,2]

1. 6
2. 7
3. 8
4. 9
5. 10

Get rows

df[3,]

A data.frame: 1 × 3

	a	b	c
	<int>	<int>	<dbl>
3	3	8	0.3914048

df[c(1,3), ]

A data.frame: 2 × 3

	a	b	c
	<int>	<int>	<dbl>
1	1	6	0.5207780
3	3	8	0.3914048

Get cell

df[2,3]

-1.56970441859343

Get sub-frame

df[c(1,3)]

A data.frame: 5 × 2

a	c
<int>	<dbl>
1	0.5207780
2	-1.5697044
3	0.3914048
4	-0.5415737
5	-0.9471250

df[c(1,3), 2:3]

A data.frame: 2 × 2

	b	c
	<int>	<dbl>
1	6	0.5207780
3	8	0.3914048