R dummies

Similar to the way that R displays vectors, [[1]] means that R is showing thefirst element of a list. Lists are extremely important concepts in R; they allowyou to combine all kinds of variables. You can read more about lists in Chapter7.In the preceding example, this list has only a single element. Yes, that’s right:The list has one element, but that element is a vector.To extract an element from a list, you have to use double square brackets.Split your pangram into words, and assign the first element to a new variable calledwords, using double-square-brackets ([[]]) subsetting, as follows:words words[1] “The” “quick” “brown” “fox” “jumps” “over” “the” “lazy” “dog”To find the unique elements of a vector, including a vector of text, you usethe unique() function. In the variable words, “the” appears twice: once inlowercase and once with the first letter capitalized. To get a list of the uniquewords, first convert words to lowercase and then use unique:> unique(tolower(words))[1] “the” “quick” “brown” “fox” “jumps” “over” “lazy”[8] “dog”Concatenating textNow that you’ve split text, you can concatenate these elements so that theyagain form a single text string.Changing text caseTo change some elements of words to uppercase, use the toupper()function:toupper(words[c(4, 9)])[1] “FOX” “DOG”To change text to lowercase, use tolower():> tolower(“Some TEXT in Mixed CASE”)