R(13), List
List can contain different types of elements: number, string, vector, and even another list. Also, the elements of List can also be matrices or functions.
create list
List is create by function list().
name elements in list
# Create a list containing a vector, a matrix and a list.
list_data <- list(c("Jan","Feb","Mar"), matrix(c(3,9,5,1,-2,8), nrow = 2), list("green",12.3))
# Give names to the elements in the list.
names(list_data) <- c("1st Quarter", "A_Matrix", "A Inner list")
# Show the list.
print(list_data)
visit elements
When visiting, we can use index. What's more, after the list is named, we can use the name to visit.
# Create a list containing a vector, a matrix and a list.
list_data <- list(c("Jan","Feb","Mar"), matrix(c(3,9,5,1,-2,8), nrow = 2),
list("green",12.3))
# Give names to the elements in the list.
names(list_data) <- c("1st Quarter", "A_Matrix", "A Inner list")
# Access the first element of the list.
print(list_data[1])
# Access the thrid element. As it is also a list, all its elements will be printed.
print(list_data[3])
# Access the list element using the name of the element.
print(list_data$A_Matrix)
manipulation elements
We can add, delete, and update list elements, as shown below. We can only add and delete elements at the end of the list. But we can update any element.
# Create a list containing a vector, a matrix and a list.
list_data <- list(c("Jan","Feb","Mar"), matrix(c(3,9,5,1,-2,8), nrow = 2), list("green",12.3))
# Give names to the elements in the list.
names(list_data) <- c("1st Quarter", "A_Matrix", "A Inner list")
# Add element at the end of the list.
list_data[4] <- "New element"
print(list_data[4])
# Remove the last element.
list_data[4] <- NULL
# Print the 4th Element.
print(list_data[4])
# Update the 3rd Element.
list_data[3] <- "updated element"
print(list_data[3])
lists merging
# Create two lists.
list1 <- list(1,2,3)
list2 <- list("Sun","Mon","Tue")
# Merge the two lists.
merged.list <- c(list1,list2)
# Print the merged list.
print(merged.list)
transfer list to vector
# Convert the lists to vectors.
v1 <- unlist(list1)
v2 <- unlist(list2)