To print a listing of all examples of a chapter, use ch5().
To run all the examples of ch5(), use example(ch5).
Examples
if (interactive()) {
# Chapter 5 - Getting Started with Reading and Writing
# Using Character Vectors for Text Data
## Assigning a value to a character vector
x <- "Hello world!"
is.character(x)
length(x)
nchar(x)
## Creating a character vector with more than one element
x <- c("Hello", "world!")
length(x)
nchar(x)
## Extracting a subset of a vector
letters
LETTERS
letters[10]
LETTERS[24:26]
tail(LETTERS, 5)
head(letters, 10)
## Naming the values in your vectors
### Looking at how named vectors work
str(islands)
islands[c("Asia", "Africa", "Antarctica")]
names(islands)[1:9]
names(sort(islands, decreasing=TRUE)[1:6])
## Creating and assigning named vectors
month.days <- c(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)
names(month.days) <- month.name
month.days
names(month.days[month.days==31])
# Manipulating Text
## String theory: Combining and splitting strings
### Splitting text
pangram <- "The quick brown fox jumps over the lazy dog"
pangram
strsplit(pangram, " ")
words <- strsplit(pangram, " ")[[1]]
words
### Changing text case
unique(tolower(words))
toupper(words[c(4, 9)])
tolower("Some TEXT in Mixed CASE")
### Concatenating text
paste("The", "quick", "brown", "fox")
paste(c("The", "quick", "brown", "fox"))
paste(words, collapse=" ")
paste(words, collapse="_")
paste(LETTERS[1:5], 1:5, sep="_", collapse="---")
paste("Sample", 1:5)
paste(c("A", "B"), c(1, 2, 3, 4), sep="-")
paste(c("A"), c(1, 2, 3, 4, 5), sep="-")
## Sorting text
sort(letters, decreasing=TRUE)
sort(words)
## Finding text inside text
### Searching for individual words
head(state.name)
### Searching by position
head(substr(state.name, start=3, stop=6))
### Searching by pattern
grep("New", state.name)
state.name[29]
state.name[grep("New", state.name)]
state.name[grep("new", state.name)]
### Searching for multiple words
state.name[grep(" ", state.name)]
state.name[grep("East", state.name)]
## Substituting text
gsub("cheap", "sheep's", "A wolf in cheap clothing")
x <- c("file_a.csv", "file_b.csv", "file_c.csv")
y <- gsub("file_", "", x)
y
gsub(".csv", "", y)
#### Extending text functionality with stringr
if (FALSE) {
install.packages("stringr")
}
library(stringr)
## Revving up with regular expressions
rwords <- c("bach", "back", "beech", "beach", "black")
grep("beach|beech", rwords)
rwords[grep("beach|beech", rwords)]
rwords[grep("be(a|e)ch", rwords)]
rwords[grep("b(e*|a*)ch", rwords)]
# Factoring in Factors
## Creating a factor
directions <- c("North", "East", "South", "South")
factor(directions)
factor(directions, levels= c("North", "East", "South", "West"))
factor(directions, levels= c("North", "East", "South", "West"), labels=c("N", "E", "S", "W"))
## Converting a factor
directions <- c("North", "East", "South", "South")
directions.factor <- factor(directions)
directions.factor
as.character(directions.factor)
as.numeric(directions.factor)
numbers <- factor(c(9, 8, 10, 8, 9))
as.character(numbers)
as.numeric(numbers)
as.numeric(as.character(numbers))
## Looking at levels
str(state.region)
levels(state.region)
levels(state.region) <- c("NE", "S", "NC", "W")
head(state.region)
nlevels(state.region)
length(levels(state.region))
levels(state.region)[2:3]
## Distinguishing data types
head(state.region)
table(state.region)
state.region
## Working with ordered factors
status <- c("Lo", "Hi", "Med", "Med", "Hi")
ordered.status <- factor(status, levels=c("Lo", "Med", "Hi"), ordered=TRUE)
ordered.status
table(status)
table(ordered.status)
}