The rowMeans() function in R can be used to calculate the mean of several rows of a matrix or data frame in R.
This function uses the following basic syntax:
#calculate row means of every column rowMeans(df) #calculate row means and exclude NA values rowMeans(df, na.rm=T) #calculate row means of specific rows rowMeans(df[1:3, ])
The following examples show how to use this syntax in practice.
Example 1: Calculate Mean of Every Row
The following code shows how to calculate the mean of every row in a data frame:
#create data frame df 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)) #view data frame df points assists rebounds blocks 1 99 33 30 1 2 91 28 28 4 3 86 31 24 11 4 88 39 24 0 5 95 34 28 2 #calculate row means rowMeans(df) [1] 40.75 37.75 38.00 37.75 39.75
Here’s how to interpret the output:
- The mean of values in the first row is 40.75.
- The mean of values in the second row is 37.75.
And so on.
Example 2: Calculate Mean of Every Row & Exclude NA’s
The following code shows how to calculate the mean of every row and exclude NA values:
#create data frame with some NA values df 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)) #view data frame df points assists rebounds blocks 1 99 33 30 1 2 91 NA 28 4 3 86 31 NA 11 4 88 39 NA 0 5 95 34 28 2 #calculate row means rowMeans(df, na.rm=T) [1] 40.75000 41.00000 42.66667 42.33333 39.75000
Example 3: Calculate Mean of Specific Rows
The following code shows how to calculate the mean values of specific rows in the data frame:
#create data frame df 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 row means for first three rows only rowMeans(df[1:3, ]) 1 2 3 40.75 37.75 38.00
We can also use the c() syntax to select specific rows:
#calculate row means for rows 1, 4, and 5
rowMeans(df[c(1, 4, 5), ])
1 4 5
40.75 37.75 39.75 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