How to Convert matrix to a list of column vectors in R ?

In this article, we will discuss how to convert a given matrix to a list of column vectors in R Programming Language. To do this we will take every column of the matrix and store that column in a list and at last print the list.

It can be done in these ways:

• Using the split() function
• Using list() with data.frame()

Method 1: Using split() function:

In this example to Convert a given matrix to a list of column vectors in R we use the split() function. 

• The split() function is used to split the data according to our requirement.
• The arguments given in the split() function are data itself and the other one is rep() function
• The rep() function is used to replicates the data and in the rep() function we give one argument i.e. nrow() so, that the sequence is generated row-wise
• In nrow() function we give the data as an argument. “each = nrow()” is used to repeat this process for each row.

Example:

R

# create matrix
M = matrix(100:112, ncol=3)

# print the matrix
display(M)

# create matrix to list off column vector
l =  split(M, rep(1:ncol(M), each = nrow(M)))

# print the list
display(l)

Output:

fig 1: Matrix

fig 2: Matrix converted to list of column vectors

Method 2: using the list() function:

In this example to Convert a given matrix to a list of column vectors in R we use the list() function 

• The list() function is used with the “as.” command. This command is used to convert the object into a list and the object can be any kind of data structure i.e. data frame, matrix, vector, etc.
• The argument in the list() function is as.data.frame. So basically, what we are doing here is? At first, we convert a matrix into the data frame by using as.data.frame() then we convert that data frame into the list and at last, print that list.
• In our case what happens is as.list() takes every single column of the data frame and put every element of data frame’s column into a list, store that lists into “l” and prints the l.

R

# creating the matrix
M = matrix(100:112, ncol = 3)

# print the matrix
display(M)

# as.list() is used to convert an object into list
# as.data.frame() is used to convert as object into
# data frame M is converted into the data frame then
# that data frame is converted into the list
l<-as.list(as.data.frame(M))

# print the list
display(l)

Output: 

fig 3: Matrix converted to list of column vectors