The **colMeans()** function in R can be used to calculate the mean of several columns of a matrix or data frame in R.

This function uses the following basic syntax:

#calculate column means of every column colMeans(df) #calculate column means and exclude NA values colMeans(df, na.rm=T) #calculate column means of specific columns colMeans(df[c('col1', 'col3', 'col4')])

The following examples show how to use this syntax in practice.

**Example 1: Calculate Mean of Every Column**

The following code shows how to calculate the mean of every column in a data frame:

#create data frame df <- data.frame(points=c(99, 91, 86, 88, 95), assists=c(33, 28, 31, 39, 34), rebounds=c(30, 28, 24, 24, 28), blocks=c(1, 4, 11, 0, 2)) #calculate column means colMeans(df) points assists rebounds blocks 91.8 33.0 26.8 3.6

**Example 2****: Calculate Mean of Every Column & Exclude NA’s**

The following code shows how to calculate the mean of every column and exclude NA values:

#create data frame with some NA values df <- data.frame(points=c(99, 91, 86, 88, 95), assists=c(33, NA, 31, 39, 34), rebounds=c(30, 28, NA, NA, 28), blocks=c(1, 4, 11, 0, 2)) #calculate column means colMeans(df, na.rm=T) points assists rebounds blocks 91.80000 34.25000 28.66667 3.60000

**Example 3: Calculate Mean of Specific Columns**

The following code shows how to calculate the mean values of specific columns in the data frame:

#create data frame df <- data.frame(points=c(99, 91, 86, 88, 95), assists=c(33, 28, 31, 39, 34), rebounds=c(30, 28, 24, 24, 28), blocks=c(1, 4, 11, 0, 2)) #calculate column means for 'points' and 'blocks' columns colMeans(df[c('points', 'blocks')]) points blocks 91.8 3.6

Note that we can also use index values to calculate the mean of specific columns:

#create data frame df <- data.frame(points=c(99, 91, 86, 88, 95), assists=c(33, 28, 31, 39, 34), rebounds=c(30, 28, 24, 24, 28), blocks=c(1, 4, 11, 0, 2)) #calculate column means for columns in position 1 and 4 colMeans(df[c(1, 4)]) points blocks 91.8 3.6

**Additional Resources**

The following tutorials explain how to perform other common functions in R:

How to Calculate Standard Deviation of Columns in R

How to Calculate the Mean by Group in R

How to Calculate the Sum by Group in R