Combining Objects
The c function combines vectors and lists
c(1, 2, 3)
## [1] 1 2 3
x <- 1:3; y <- 101:103
c(x, y)
## [1] 1 2 3 101 102 103
iris$Species[1:8]
## [1] setosa setosa setosa setosa setosa setosa setosa setosa
## Levels: setosa versicolor virginica
The cbind and rbind functions can be used to append columns and rows, respecively.
ma <- cbind(x, y)
ma
## x y
## [1,] 1 101
## [2,] 2 102
## [3,] 3 103
rbind(ma, ma)
## x y
## [1,] 1 101
## [2,] 2 102
## [3,] 3 103
## [4,] 1 101
## [5,] 2 102
## [6,] 3 103
Accessing Dimensions of Objects
Length and dimension information of objects
length(iris$Species)
## [1] 150
dim(iris)
## [1] 150 5
Accessing Name Slots of Objects
Accessing row and column names of 2D objects
rownames(iris)[1:8]
## [1] "1" "2" "3" "4" "5" "6" "7" "8"
colnames(iris)
## [1] "Sepal.Length" "Sepal.Width" "Petal.Length" "Petal.Width" "Species"
Return name field of vectors and lists
names(myVec)
## [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V" "W" "X"
## [25] "Y" "Z"
names(myL)
## [1] "name" "wife" "no.children" "child.ages"
Sorting Objects
The function sort returns a vector in ascending or descending order
sort(10:1)
## [1] 1 2 3 4 5 6 7 8 9 10
The function order returns a sorting index for sorting an object
sortindex <- order(iris[,1], decreasing = FALSE)
sortindex[1:12]
## [1] 14 9 39 43 42 4 7 23 48 3 30 12
iris[sortindex,][1:2,]
## Sepal.Length Sepal.Width Petal.Length Petal.Width Species
## 14 4.3 3.0 1.1 0.1 setosa
## 9 4.4 2.9 1.4 0.2 setosa
sortindex <- order(-iris[,1]) # Same as decreasing=TRUE
Sorting multiple columns
iris[order(iris$Sepal.Length, iris$Sepal.Width),][1:2,]
## Sepal.Length Sepal.Width Petal.Length Petal.Width Species
## 14 4.3 3.0 1.1 0.1 setosa
## 9 4.4 2.9 1.4 0.2 setosa