To print a listing of all examples of a chapter, use ch7().
To run all the examples of ch7(), use example(ch7).
Examples
if (interactive()) {
# Chapter 7
# Working in More Dimensions
# Adding a Second Dimension
## Discovering a new dimension
### Creating your first matrix
first.matrix <- matrix(1:12, ncol=4)
first.matrix
matrix(1:12, ncol=4, byrow=TRUE)
### Looking at the properties
str(first.matrix)
dim(first.matrix)
length(first.matrix)
my.array <- array(1:24, dim=c(3,4,2))
baskets.of.Granny <- c(12,4,5,6,9,3)
baskets.of.Geraldine <- c(5,4,2,4,12,9)
baskets.team <- rbind(baskets.of.Granny, baskets.of.Geraldine)
attributes(my.array)
attr(baskets.team,'season') <- '2010-2011'
attr(baskets.team,'season')
attr(baskets.team,'season') <- NULL
## Combining vectors into a matrix
baskets.of.Granny <- c(12,4,5,6,9,3)
baskets.of.Geraldine <- c(5,4,2,4,12,9)
baskets.team <- rbind(baskets.of.Granny, baskets.of.Geraldine)
baskets.team
cbind(1:3, 4:6, matrix(7:12, ncol=2))
# Using the Indices
## Extracting values from a matrix
### Using numeric indices
first.matrix[1:2, 2:3]
first.matrix[2:3,]
### Dropping values using negative indices
first.matrix[-2,-3]
nr <- nrow(first.matrix)
id <- nr*2+2
first.matrix[-id]
first.matrix[-(2 * nrow(first.matrix) + 2)]
### Juggling dimensions
first.matrix[-c(1, 3), ]
first.matrix[2, , drop=FALSE]
## Replacing values in a matrix
first.matrix[3, 2] <- 4
first.matrix
first.matrix[2, ] <- c(1,3)
first.matrix
first.matrix[1:2, 3:4] <- c(8,4,2,1)
first.matrix
# Naming Matrix Rows and Columns
## Changing the row and column names
rownames(baskets.team) <- c('Granny','Geraldine')
rownames(baskets.team)
colnames(baskets.team) <- c('1st','2nd','3th','4th','5th','6th')
baskets.team
colnames(baskets.team)[3] <- '3rd'
baskets.copy <- baskets.team
colnames(baskets.copy) <- NULL
baskets.copy
## Using names as indices
baskets.team[, c("2nd","5th")]
baskets.team["Granny",]
# Calculating with Matrices
## Using standard operations with matrices
first.matrix + 4
second.matrix <- matrix(1:3, nrow=3, ncol=4)
first.matrix + second.matrix
# first.matrix + second.matrix[,1:3] # gives error for illustration
# Error in first.matrix + second.matrix[, 1:3] : non-conformable arrays
first.matrix + 1:3
## Calculating row and column summaries
rowSums(baskets.team)
## Doing matrix arithmetic
### Transposing a matrix
t(first.matrix)
t(1:10)
t(first.matrix[2,])
### Inverting a matrix
square.matrix <- matrix(c(1,0,3,2,2,4,3,2,1),ncol=3)
solve(square.matrix)
### Multiplying two matrices
first.matrix %*% t(second.matrix)
first.matrix %*% 1:4
1:3 %*% first.matrix
# Adding More Dimensions
## Creating an array
### Using the creator functions
my.array <- array(1:24, dim=c(3,4,2))
my.array
### Changing the dimensions of a vector
my.vector <- 1:24
dim(my.vector) <- c(3,4,2)
identical(my.array, my.vector)
## Using dimensions to extract values
my.array[2,3,1]
my.array[, 3, 2, drop=FALSE]
my.array[2, , ]
# Combining Different Types of Values in a Data Frame
## Creating a data frame from a matrix
### Using the function as.data.frame
baskets.df <- as.data.frame(t(baskets.team))
### Looking at the structure of a data frame
baskets.df
str(baskets.df)
### Counting values and variables
nrow(baskets.df)
length(baskets.df)
## Creating a data frame from scratch
### Making a data frame from vectors
employee <- c('John Doe','Peter Gynn','Jolie Hope')
salary <- c(21000, 23400, 26800)
startdate <- as.Date(c('2010-11-1','2008-3-25','2007-3-14'))
employ.data <- data.frame(employee, salary, startdate)
str(employ.data)
### Keeping characters as characters
employ.data <- data.frame(employee, salary, startdate, stringsAsFactors=FALSE)
str(employ.data)
## Naming variables and observations
### Working with variable names
colnames(employ.data)
names(employ.data)
names(employ.data)[3] <- 'firstday'
names(employ.data)
### Naming observations
rownames(employ.data)
rownames(employ.data) <- c('Chef','BigChef','BiggerChef')
employ.data
# Manipulating Values in a Data Frame
## Extracting variables, observations, and values
### Pretending it's a matrix
baskets.df['3rd', 'Geraldine']
baskets.df[, 1]
str(baskets.df[, 1, drop=FALSE])
### Putting your dollar where your data is
baskets.df$Granny
## Adding observations to a data frame
### Adding a single observation
result <- rbind(baskets.df, c(7,4))
result
baskets.df <- rbind(baskets.df,'7th' = c(7,4))
baskets.df
### Adding a series of new observations using rbind
new.baskets <- data.frame(Granny=c(3,8),Geraldine=c(9,4))
rownames(new.baskets) <- c('8th','9th')
baskets.df <- rbind(baskets.df, new.baskets)
### Adding a series of values using indices
baskets.df[c('8th','9th'), ] <- matrix(c(3,8,9,4), ncol=2)
baskets.df[c('8th','9th'), ] <- c(3,8,9,4)
## Adding variables to a data frame
### Adding a single variable
baskets.of.Gabrielle <- c(11,5,6,7,3,12,4,5,9)
baskets.df$Gabrielle <- baskets.of.Gabrielle
head(baskets.df, 4)
### Adding multiple variables using cbind
new.df <- data.frame(
Gertrude = c(3,5,2,1,NA,3,1,1,4),
Guinevere = c(6,9,7,3,3,6,2,10,6)
)
head(cbind(baskets.df, new.df), 4)
# Combining Different Objects in a List
## Creating a list
### Creating an unnamed list
baskets.list <- list(baskets.team, '2010-2011')
baskets.list
### Creating a named list
baskets.nlist <- list(scores=baskets.team, season='2010-2011')
baskets.nlist
### Playing with the names of elements
names(baskets.nlist)
### Getting the number of elements
length(baskets.list)
## Extracting elements from lists
### Using [[]]
baskets.list[[1]]
baskets.nlist[['scores']]
### Using []
baskets.list[-1]
baskets.nlist[names(baskets.nlist)=='season']
## Changing the elements in lists
### Changing the value of elements
baskets.nlist[[1]] <- baskets.df
baskets.nlist[['scores']] <- baskets.df
baskets.nlist$scores <- baskets.df
baskets.nlist[1] <- list(baskets.df)
baskets.list[1:2] <- list(baskets.df, '2009-2010')
### Removing elements
baskets.nlist[[1]] <- NULL
baskets.nlist$scores <- NULL
baskets.nlist['scores'] <- NULL
baskets.nlist <- list(scores=baskets.df, season='2010-2011')
baskets.nlist['scores'] <- list(NULL)
baskets.nlist
### Adding extra elements using indices
baskets.nlist$players <- c('Granny','Geraldine')
baskets.nlist[['players']] <- c('Granny','Geraldine')
baskets.nlist['players'] <- list(c('Granny','Geraldine'))
baskets.list[[3]] <- c('Granny','Geraldine')
baskets.list[3] <- list(c('Granny','Geraldine'))
### Combining lists
baskets.list <- list(baskets.team,'2010-2011')
players <- list(rownames(baskets.team))
c(baskets.list, players)
## Reading the output of str() for lists
str(baskets.list)
## Seeing the forest through the trees
}