R list can contain a string, a numeric variable, a vector, a matrix, an array, a function, and even another list.<\/p>\n
In this R list tutorial, we will explore the lists in the R programming language. We will learn how to create them and how to name their components. We will also learn how to index them, and how to manipulate their components. Our schedule is packed, so, let\u2019s get going!<\/p>\n
How to Create Lists in R?<\/h2>\n
We can use the list()<\/strong> function to create a list.<\/p>\n For example:<\/strong><\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n Another way to create a list is to use the c()<\/strong> function. The c() function coerces<\/strong> elements into the same type, so, if there is a list amongst the elements, then all elements are turned into components of a list.<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n Notice that the vector and the list inside the c() function are not separate vector and list inside list2. Instead, their components have become list2\u2019s components. The c() function breaks down any objects with multiple elements.<\/p>\n The c() function can combine two or more lists into one as well.<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n We can name a list\u2019s components while creating it. This is similar to naming vector elements.<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n We can also name a list\u2019s components after its creation by using the names() function.<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n naming R list details<\/p><\/div>\n In a list, components are always numbered<\/strong>. We can refer to the components using those in double square brackets. So, we can refer to list1\u2019s components as list1[[1]], list1[[2]], etc..<\/p>\n If there are elements within a list\u2019s components, then we can refer to them as list1[[1]][1] and so on.<\/p>\n We can refer to an R<\/a> list\u2019s components in a similar fashion to vectors by using logical, integer or character vectors.<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n We can change existing components in a list. We can also add new components and delete existing ones as well.<\/p>\n We can modify a component by accessing them through indexing and reassigning<\/strong> the new value.<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n> list1 <- list(2, \"hello\", c(3,5,4), 1:5, list(FALSE, c(\"this\", \"is\",\"a\",\"list\"),c(FALSE,TRUE,TRUE,TRUE,FALSE))) \n> str(list1) #displays the structure of an object<\/pre>\n
\n$ : num 2
\n$ : chr “hello”
\n$ : num [1:3] 3 5 4
\n$ : int [1:5] 1 2 3 4 5
\n$ :List of 3
\n..$ : logi FALSE
\n..$ : chr [1:4] “this” “is” “a” “list”
\n..$ : logi [1:5] FALSE TRUE TRUE TRUE FALSE<\/div>\n![\"R](\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2020\/01\/lists-creating-a-list-list1.png\")
<\/a><\/p>\n> list2 <- c(c(1,2),\"techvidvan\",list(c(FALSE,TRUE),rep(c(1,2,3),4))) \n> str(list2)<\/pre>\n
\n$ : num 1
\n$ : num 2
\n$ : chr “techvidvan”
\n$ : logi [1:2] FALSE TRUE
\n$ : num [1:12] 1 2 3 1 2 3 1 2 3 1 …<\/div>\n<\/a><\/p>\n> list3 <- c(list1,list2) #combines list1 and list2 into list3 \n> str(list3)<\/pre>\n
\n$ : num 2
\n$ : chr “hello”
\n$ : num [1:3] 3 5 4
\n$ : int [1:5] 1 2 3 4 5
\n$ :List of 3
\n..$ : logi FALSE
\n..$ : chr [1:4] “this” “is” “a” “list”
\n..$ : logi [1:5] FALSE TRUE TRUE TRUE FALSE
\n$ : num 1
\n$ : num 2
\n$ : chr “techvidvan”
\n$ : logi [1:2] FALSE TRUE
\n$ : num [1:12] 1 2 3 1 2 3 1 2 3 1 …<\/div>\n<\/a><\/p>\nHow to Name R List\u2019s Components?<\/h3>\n
> named_list1 <- list(\"name\"=\"Bob\",\"wife name\"=\"julie\",\"age\"= 35,\"children\"=3,\"children age\"=c(4,7,9)) \n> str(named_list1)<\/pre>\n
\n$ name : chr “Bob”
\n$ wife name : chr “julie”
\n$ age : num 35
\n$ children : num 3
\n$ children age: num [1:3] 4 7 9<\/div>\n<\/a><\/p>\n> details <- list(\"jim\",\"jenny\",42,2,c(14,17))\n> str(details)<\/pre>\n
\n$ : chr “jim”
\n$ : chr “jenny”
\n$ : num 42
\n$ : num 2
\n$ : num [1:2] 14 17<\/div>\n> names(details) <- c(\"name\",\"wife name\",\"age\",\"children\", \"children age\")\n> str(details)<\/pre>\n
\n$ name : chr “jim”
\n$ wife name : chr “jenny”
\n$ age : num 42
\n$ children : num 2
\n$ children age: num [1:2] 14 17<\/div>\n<\/a>Indexing a List<\/h3>\n
Using logical vectors:<\/h4>\n
> list2[c(F,F,T,F,T)] #index using logical vector<\/pre>\n
\n[1] “techvidvan”[[2]]
\n[1] 1 2 3 1 2 3 1 2 3 1 2 3<\/div>\n<\/a><\/p>\nUsing positive integers:<\/h4>\n
> list3[c(3:4)] #index using positive integer vector<\/pre>\n
\n[1] 3 5 4
\n[[2]]
\n[1] 1 2 3 4 5<\/div>\n<\/a><\/p>\nUsing negative integers:<\/h4>\n
> list1[c(-2,-3,-5)] #index using negative integers\n<\/pre>\n
\n[1] 2[[2]]
\n[1] 1 2 3 4 5<\/div>\n<\/a><\/p>\nUsing character vectors for named lists:<\/h4>\n
> named_list1[c(\"name\",\"age\")] #index using character vector<\/pre>\n
\n[1] “Bob”$age
\n[1] 35<\/div>\n<\/a><\/p>\nHow to Manipulate list in R?<\/h3>\n
Modifying a component:<\/h4>\n
> details[[\"name\"]] <- \"harry\" \n> str(details)<\/pre>\n
\n$ name : chr “harry”
\n$ wife name : chr “jenny”
\n$ age : num 42
\n$ children : num 2
\n$ children age: num [1:2] 14 17<\/div>\n