Collections and Data Structures
Lists
Lists in R are ordered collections of data that can be of different classes.
Creating Lists
New list (empty)
listname <- list()
New list (misc)
listname <- list(1L, "abc", 10.3)
Accessing List Elements
Access an element
list[position]
Change a value
list[position] <- newvalue
See number of values in a list
length(list)
See if item is present in a list
item %in% list
Adding and Removing List Elements
Add item to a list
append(list)
Add item to a list at a specific position
append(list, after=index number)
Remove item from list
newlist <- list[-index number]
Inputs:
#Create list
mylist <- list("apple", "peach", "plum")
#Access the second element of a list
mylist[2]
#Change the value of the first element of a list
mylist[1] <- "banana"
mylist
#See the number of values in a list
length(mylist)
#Check if item exists in list
"plum" %in% mylist
#Add an item to the list
append(mylist, "orange", after=2)
mylist
#Remove an item at index=3 from a list
mylist <- list("apple", "peach", "plum")
newlist <- mylist[-3]
newlistOutputs:
#Access the second element of a list
"peach"
#Change the value of the first element of a list
[[1]]
[1] "banana"
[[2]]
[1] "peach"
[[3]]
[1] "plum"
#See the number of values in a list
3
#Check if item exists in list
TRUE
#Add an item to the list
[[1]]
[1] "banana"
[[2]]
[1] "peach"
[[3]]
[1] "orange"
[[4]]
[1] "plum"
#Remove an item from a list
[[1]]
[1] "apple"
[[2]]
[1] "peach"Matrices
Creating Matrices
New matrix (empty)
matrixname <- matrix()
New matrix (numbers)
matrixname <- matrix(data, nrow=, ncol=)
New matrix (strings)
matrixname <- matrix(data, nrow=, ncol=)
Accessing Matrix Elements
Access a matrix element
matrix[row position, column position]
Access an entire row
matrix[row position,]
Access an entire column
matrix[,column position]
Adding and Removing Matrix Elements
Create an additional row
rbind(matrix, values for new row)
Create an additional column
cbind(matrix, values for new column)
Inputs:
#Creating array
heart <- matrix(c("left atrium", "left ventricle",
"right atrium", "right ventricle"), nrow=2, ncol=2)
heart
#Access element at row=1, column=2
heart[1,2]
#Access entire row 1
heart[1,]
#Access entire column 2
heart[,2]
#Create new row
heart1 <- rbind(heart, c("x", "x"))
heart1
#Create new column
heart2 -< cbind(heart1, c("y", "y", "z"))
heart2Outputs:
#Creating array
[,1] [,2]
[1,] "left atrium" "right atrium"
[2,] "left ventricle" "right ventricle"
#Access element at row=1, column=2
"right atrium"
#Access entire row 1
"left atrium" "right atrium"
#Access entire column 2
"right atrium" "right ventricle"
#Create new row
[,1] [,2]
[1,] "left atrium" "right atrium"
[2,] "left ventricle" "right ventricle"
[3,] "x" "x"
#Create new column
[,1] [,2] [,3]
[1,] "left atrium" "right atrium" "y"
[2,] "left ventricle" "right ventricle" "y"
[3,] "x" "x" "z" Arrays
Creating Arrays
New array (empty)
arrayname <- array()
New array (numbers)
arrayname <- array(data, dim(nrow=, ncol=, ndim=)
New array (strings
arrayname <- array(data, dim(nrow=, ncol=, ndim=)
Array Elements
Access an array element
array[row position, column position, dimension]
Check if an item exists
value %in% array
Sort array increasing
sort(array)
Sort array decreasing
sort(array, decreasing = TRUE)
Inputs:
#Creating array
a <- array(c(1:20),dim = c(4,4,2))
#Access element at row=4, column=4, dimension=1
a[4, 4, 1]
#Check if item exists in array
2 %in% a
#Sort increasing
b <- array(c(16:1),dim = c(4,4,1))
sort(b)
#Sort decreasing
c <- array(c(1:16),dim = c(4,4,1))
sort(c, decreasing = TRUE)Outputs:
#Access element at row=4, column=4, dimension=1
16
#Check if item exists in array
TRUE
#Sort increasing
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
#Sort decreasing
16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1Resources
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