How to Use rowMeans() Function in R

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R rowMeans() function is used to calculate the mean of each row of a data frame or matrix.

Syntax

rowMeans(x, na.rm = FALSE)

Parameters

  1. x: It is an array of two or more dimensions containing numeric, complex, integer, or logical values or a numeric data frame.
  2. na.rm: It is a logical argument. If TRUE, NA values are ignored.

Example 1: Calculating the mean of every row of a data frame

Figure of Calculating the mean of every row of a data frame

# Create data frame
df <- data.frame(
  player1 = c(11, 55, 99, 444, 888),
  player2 = c(22, 66, 111, 555, 999),
  player3 = c(33, 77, 222, 666, 11),
  player4 = c(44, 88, 333, 777, 22)
)

# Calculating the mean of every row using rowMeans() function
rowMeans(df)

Output

[1] 27.50  71.50  191.25  610.50  480.00

We calculated the mean of the values across each row using the rowMeans() function, effectively providing the average value for each player across the columns.

Example 2: Calculating the mean of every row and excluding NA values

Calculating the mean of every row of data frame containing NA values

As you can see from the figure, we get the output NA for every row because every row contains NA values.

# Create a data frame.
df <- data.frame(
  col1 = c(NA, 2, 3),
  col2 = c(4, NA, 6),
  col3 = c(7, 8, NA)
)

# Calculate the mean of data frame
rowMeans(df)

Output

[1] NA NA NA

You can exclude NA values while calculating the mean of every row by passing the na.rm = TRUE parameter to the rowMeans() function.

Figure of handling missing values while using rowMeans() function

# Create a data frame.
df <- data.frame(
  col1 = c(NA, 2, 3),
  col2 = c(4, NA, 6),
  col3 = c(7, 8, NA)
)

# Calculate the mean of data frame
rowMeans(df, na.rm = TRUE)

Output

[1] 5.5   5.0   4.5

Example 3: Calculating the mean of specific rows

Figure of calculating the mean of specific rows of data frame

# Create a data frame.
df <- data.frame(
  col1 = c(1, 2, 3),
  col2 = c(4, 5, 6),
  col3 = c(7, 8, 9)
)
rowMeans(df[c(1, 3), ])

Output

  1   3 
  4   6

From the output and figure, you can see that for row 1, the mean is 4, and for row 2, the mean is 6.

Example 4: Calculating the mean of every row of the matrix

Figure of Calculating the mean of every row of the matrix

# Create a matrix.
mat <- matrix(1:9, 3, 3)
print(mat)

# Calculate the mean of each row.
cat("The mean of every row of matrix: ", rowMeans(mat), "\n")

Output

The mean of every row of matrix: 4  5  6

See also

colMeans() function

rowSums() function

colSums() function

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