What are strings?

The simplest distinction:

• Character: a symbol in a written language, like letters, numerals, punctuation, space, etc.

• String: a sequence of characters bound together

class("r")

## [1] "character"

class("Ryan")

## [1] "character"

Why do we care?

• A lot of interesting data out there is in character form!
• Webpages, emails, surveys, logs, search queries, etc.
• Even if you just care about numbers eventually, you’ll need to understand how to get numbers from text

How to make strings

Just use double quotes or single quotes and type anything in between

str.1 = "Statistical"
str.2 = 'Computing'

We often prefer double quotes to single quotes, because then we can use apostrophes

str.3 = "isn't that bad"

Whitespaces

Whitespaces count as characters and can be included in strings:

• " " for space
• "\n" for newline
• "\t" for tab

message = "Dear Mr. Carnegie,\n\nThanks for the great school!\n\nSincerely, Ryan"

Printing strings

To print to the console, use the cat() function

message

## [1] "Dear Mr. Carnegie,\n\nThanks for the great school!\n\nSincerely, Ryan"

cat(message)

## Dear Mr. Carnegie,
## 
## Thanks for the great school!
## 
## Sincerely, Ryan

Vectors of strings

The character is a basic data type in R (like numeric, or logical), so we can make vectors of out them. Just like we would with numbers

str.vec = c(str.1, str.2, str.3) # Collect 3 strings
str.vec # All elements of the vector

## [1] "Statistical"    "Computing"      "isn't that bad"

str.vec[3] # The 3rd element

## [1] "isn't that bad"

str.vec[-(1:2)] # All but the 1st and 2nd

## [1] "isn't that bad"

head(str.vec, 2) # The first 2 elements

## [1] "Statistical" "Computing"

tail(str.vec, 2) # The last 2 elements

## [1] "Computing"      "isn't that bad"

rev(str.vec) # Reverse the order

## [1] "isn't that bad" "Computing"      "Statistical"

Matrices of strings

Same idea with matrices

str.mat = matrix("", 2, 3) # Build an empty 2 x 3 matrix
str.mat[1,] = str.vec # Fill the 1st row with str.vec
str.mat[2,1:2] = str.vec[1:2] # Fill the 2nd row, only entries 1 and 2, with those of str.vec
str.mat[2,3] = "isn't a fad" # Fill the 2nd row, 3rd entry, with a new string
str.mat # All elements of the matrix

##      [,1]          [,2]        [,3]            
## [1,] "Statistical" "Computing" "isn't that bad"
## [2,] "Statistical" "Computing" "isn't a fad"

t(str.mat) # Transpose of the matrix

##      [,1]             [,2]         
## [1,] "Statistical"    "Statistical"
## [2,] "Computing"      "Computing"  
## [3,] "isn't that bad" "isn't a fad"

Converting other data types to strings

Easy! Make things into strings with as.character()

as.character(0.8)

## [1] "0.8"

as.character(0.8e+10)

## [1] "8e+09"

as.character(1:5)

## [1] "1" "2" "3" "4" "5"

as.character(TRUE)

## [1] "TRUE"

Converting strings to other data types

Not as easy! Depends on the given string, of course

as.numeric("0.5")

## [1] 0.5

as.numeric("0.5 ")

## [1] 0.5

as.numeric("0.5e-10")

## [1] 5e-11

as.numeric("Hi!")

## Warning: NAs introduced by coercion

## [1] NA

as.logical("True")

## [1] TRUE

as.logical("TRU")

## [1] NA

as.numeric(c("0.5", "TRUE"))

## Warning: NAs introduced by coercion

## [1] 0.5  NA

Converting to lower or upper case

Use the tolower() or toupper() functions

tolower("I'M NOT ANGRY I SWEAR")

## [1] "i'm not angry i swear"

toupper("Mom, I don't want my veggies")

## [1] "MOM, I DON'T WANT MY VEGGIES"

toupper("Hulk, sMasH")

## [1] "HULK, SMASH"