Week 13 Code Along 12

Ch20 Vectors

1 Introduction

2 Vector basics

3 Important types of atomic vector

4 Using atomic vectors

sample(10) + 10

##  [1] 14 18 17 11 20 15 12 13 19 16

1:10 + 1:2

##  [1]  2  4  4  6  6  8  8 10 10 12

1:10 + 1:3

## Warning in 1:10 + 1:3: longer object length is not a multiple of shorter object
## length

##  [1]  2  4  6  5  7  9  8 10 12 11

data.frame(a = 1:10, b = 1:2)

##     a b
## 1   1 1
## 2   2 2
## 3   3 1
## 4   4 2
## 5   5 1
## 6   6 2
## 7   7 1
## 8   8 2
## 9   9 1
## 10 10 2

# data.frame(a = 1:10, b = 1:3)

x <- sample(10)
x

##  [1]  8  1  5  3  7  4 10  6  2  9

x[c(5, 7)]

## [1]  7 10

x[x>5]

## [1]  8  7 10  6  9

5 Recursive vectors (lists)

a <- list(a = 1:3, b = "a string", c = pi, d = list(-1, -5))
a

## $a
## [1] 1 2 3
## 
## $b
## [1] "a string"
## 
## $c
## [1] 3.141593
## 
## $d
## $d[[1]]
## [1] -1
## 
## $d[[2]]
## [1] -5

a[1:2]

## $a
## [1] 1 2 3
## 
## $b
## [1] "a string"

a[[4]]

## [[1]]
## [1] -1
## 
## [[2]]
## [1] -5

a[[4]][2]

## [[1]]
## [1] -5

a[[4]][[2]]

## [1] -5

6 Attributes

7 Augmented vectors

Ch21 Iteration

1 Introduction

2 For loops

# example from the cheatsheet
for (i in 1:4){
    j <- i + 10
    print(j)
}

## [1] 11
## [1] 12
## [1] 13
## [1] 14

# example 1: numeric calculation - add 10 
x <- 11:15

for (i in seq_along(x)){
    j <- x[i] + 10
    print(j)
}

## [1] 21
## [1] 22
## [1] 23
## [1] 24
## [1] 25

# save output
y <- vector("integer", length(x))

for (i in seq_along(x)){
    y[i] <- x[i] + 10
    print(y[i])
}

## [1] 21
## [1] 22
## [1] 23
## [1] 24
## [1] 25

# output
y

## [1] 21 22 23 24 25

# example 2: string operation - extract first letter
x <- c("abc", "xyz")

y <- vector("character", length(x))

for (i in seq_along(x)){
    y[i] <- x[i] %>% str_extract("[a-z]")
    print(y[i])
}

## [1] "a"
## [1] "x"

# output
y

## [1] "a" "x"

3 The map functions

# example 1: numeric calculation - add 10 
x <- 11:15

y <- vector("integer", length(x))

for (i in seq_along(x)){
    y[i] <- x[i] + 10
    print(y[i])
}

## [1] 21
## [1] 22
## [1] 23
## [1] 24
## [1] 25

# output
y

## [1] 21 22 23 24 25

# using map function
x

## [1] 11 12 13 14 15

map(.x = x, .f = ~.x + 10)

## [[1]]
## [1] 21
## 
## [[2]]
## [1] 22
## 
## [[3]]
## [1] 23
## 
## [[4]]
## [1] 24
## 
## [[5]]
## [1] 25

map_dbl(.x = x, .f = ~.x + 10)

## [1] 21 22 23 24 25

add_10 <- function(x) {x + 10}
11 %>% add_10()

## [1] 21

map_dbl(.x = x, .f = add_10)

## [1] 21 22 23 24 25

4 Dealing failure

5 Mapping over multiple arguments