Calculate the Mean of each Column of a Matrix or Array in R Programming – colMeans() Function

colMeans() function in R Language is used to compute the mean of each column of a matrix or array.

Syntax: colMeans(x, dims = 1)

Parameters:
x: array of two or more dimensions, containing numeric, complex, integer or logical values, or a numeric data frame
dims: integer value, which dimensions are regarded as ‘columns’ to sum over. It is over dimensions 1:dims.

Example 1:

# R program to illustrate
# colMeans function

# Initializing a matrix with
# 3 rows and 3 columns
x <- matrix(rep(1:9), 3, 3)

# Getting matrix representation
x

# Calling the colMeans() function
colMeans(x)

Output:

     [, 1] [, 2] [, 3]
[1, ]    1    4    7
[2, ]    2    5    8
[3, ]    3    6    9

[1] 2 5 8

Example 2:

# R program to illustrate
# colMeans function

# Initializing a 3D array
x <- array(1:12, c(2, 3, 3))

# Getting the array representation
x

# Calling the colMeans() function

# for dims = 1, x[, 1, 1], x[, 2, 1], x[, 3, 1],
# x[, 1, 2] ... are columns
colMeans(x, dims = 1)

# for dims = 2, x[,,1], x[,,2], x[,,3]
# are columns
colMeans(x, dims = 2)

Output:

,, 1

     [, 1] [, 2] [, 3]
[1, ]    1    3    5
[2, ]    2    4    6,, 2

     [, 1] [, 2] [, 3]
[1, ]    7    9   11
[2, ]    8   10   12,, 3

     [, 1] [, 2] [, 3]
[1, ]    1    3    5
[2, ]    2    4    6

     [, 1] [, 2] [, 3]
[1, ]  1.5  7.5  1.5
[2, ]  3.5  9.5  3.5
[3, ]  5.5 11.5  5.5

[1] 3.5 9.5 3.5