Ch20 Vectors

Introduction

Vector basics

Important Types of Automic Vectors

Using Automic Vectors

sample(10) + 10
##  [1] 17 16 13 19 12 15 18 11 20 14
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]  9  8  7  6  3  2  4  5 10  1
x[c(5, 7)]
## [1] 3 4
x[x>5] 
## [1]  9  8  7  6 10

Recursive Vectors

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

Attributes

x <- 1:10
attr(x, "greeting")
## NULL
attr(x, "greeting") <- "Hi!"
attr(x, "farewell") <- "Bye!"
attributes(x)
## $greeting
## [1] "Hi!"
## 
## $farewell
## [1] "Bye!"
as.Date
## function (x, ...) 
## UseMethod("as.Date")
## <bytecode: 0x000001d14b2661c8>
## <environment: namespace:base>
methods("as.Date")
## [1] as.Date.character   as.Date.default     as.Date.factor     
## [4] as.Date.numeric     as.Date.POSIXct     as.Date.POSIXlt    
## [7] as.Date.vctrs_sclr* as.Date.vctrs_vctr*
## see '?methods' for accessing help and source code
getS3method("as.Date", "default")
## function (x, ...) 
## {
##     if (inherits(x, "Date")) 
##         x
##     else if (is.null(x)) 
##         .Date(numeric())
##     else if (is.logical(x) && all(is.na(x))) 
##         .Date(as.numeric(x))
##     else stop(gettextf("do not know how to convert '%s' to class %s", 
##         deparse1(substitute(x)), dQuote("Date")), domain = NA)
## }
## <bytecode: 0x000001d14b752868>
## <environment: namespace:base>

Augmented Vectors

Factors

x <- factor(c("ab", "cd", "ab"), levels = c("ab", "cd", "ef"))
typeof(x)
## [1] "integer"
attributes(x)
## $levels
## [1] "ab" "cd" "ef"
## 
## $class
## [1] "factor"

Ch21 Iteration

Introduction

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"

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