How to Calculate Mean in R

Mean means the arithmetic average of a number in mathematics. An average is the sum of total numbers divided by the count of the numbers.

To calculate the arithmetic mean of a vector or dataset in R, use the mean() function.

The above figure shows the simplest example of the mean, which returns 2.5.

Syntax

mean(x, na.rm)

Parameters

Example 1: Calculating the mean of a vector

In the above figure, we calculated the mean of the vector containing seven elements.

vec <- c(11, 21, 19, 18, 51, 51, 71)

# Calculating average using mean() 
mean(vec)

Output

[1] 34.57143

Example 2: Calculating the mean of a data frame column

The above figure returns the mean of DataFrame’s price column.

df <- data.frame(
  id = c(11, 22, 33, 44, 55),
  price = c(19, 46, 21, 11, 18)
)

# Calculate mean of DataFrame column
mean_of_col <- mean(df$price)
mean_of_col

Output

[1] 23

Example 3: Excluding NA values

If your data frame contains NA values, it does not exclude them by default and returns NA as an output.

This is a default principle of missing or unknown values that makes the mean undefined or not meaningful.

df <- data.frame(
  id = c(11, 22, 33, 44, NA),
  price = c(19, 46, 21, 11, NA)
)

# Calculate mean of DataFrame column
mean_of_col <- mean(df$price)
mean_of_col

Output

[1] NA

In the above figure, we passed the na.rm = TRUE to the mean() function to skip the NA value while calculating the mean of the remaining column values.

df <- data.frame(
  id = c(1, 2, 3, 4, NA),
  price = c(11, 22, 33, 44, NA)
)

# Calculate mean of DataFrame column
mean_of_col <- mean(df$price, na.rm = TRUE)
mean_of_col

Output

[1] 24.5

In the above code example, we calculated the mean value of the price column’s (11, 22, 33, 44) values.

Example 4: Plotting of mean

# Generating 10 random numbers from a standard normal distribution
data <- rnorm(10)

# Calculate the mean
data_mean <- mean(data)

# Plotting the data using base R graphics
plot(1:10, data, pch=19, col="blue", ylim=c(min(data) - 1, max(data) + 1), 
     xlab="Index", ylab="Value", main="Scatter Plot with Mean Overlay")
abline(h=data_mean, col="red", lwd=2) # Overlaying the mean
grid(col="gray")
legend("topright", legend=paste("Mean =", round(data_mean, 2)), col="red", lwd=2)

Output

The above data visualization plot shows how to plot data points but also how to enhance a plot with additional elements like mean lines, legends, and grid lines for better readability and interpretation.