The mean() is a generic function in R that is used to calculate the arithmetic mean or average of a Vector or DataFrame column. This function accepts a vector as input and returns the average as a numeric value.

In simple words mean or average is calculated by **adding up all the values and dividing the sum by the number of values**. For example, the mean of the numbers 6, 7, 8 is 7 since 6 + 7 + 8 = 21 and 21 divided by 3 results in 7.

## 1. Syntax of mean()

Following is the syntax of the mean() function.

```
# Syntax
mean(x, …)
# S3 method for default
mean(x, trim = 0, na.rm = FALSE, …)
```

`x`

– It is an input vector of type Numeric.`trim`

– Used to drop some observations from both ends of the sorted vector.`na.rm`

– Defaults to FALSE. When TRUE, it ignores NA value.

## 2. R Mean of DataFrame Column

mean() in R is a base function that is used to calculate the arithmetic mean of a numeric Vector. Since every DataFrame column is a Vector, let’s calculate the mean of a DataFrame column.

```
# Create Data Frame
df <- data.frame(id=c(11,22,33,44,55),
price=c(144,NA,321,567,567))
df
# Calculate mean of DataFrame column
res <- mean(df$id)
res
```

Yields below output.

Calculating the mean on a column that has `NA`

values results in NA, you need to ignore the NA to get the right result. Let’s calculate the mean on the column that has NA values by using the `na.rm`

param to ignore NA values. On our DataFrame, we have a column `price`

that has NA values.

```
# Calculate mean of DataFrame column
# With out ignoring NA
mean(df$price)
# Output
# [1] NA
# Calculate mean of DataFrame column
# Ignoring NA
mean(df$price, na.rm=TRUE)
# Output
# [1] 399.75
```

## 3. Mean of R Vector

Similarly, let’s calculate the mean or average of a Vector. The following example demonstrates calculating mean of Vector with out NA and with NA values.

```
# Calculate mean of Vector
vec = c(6,7,8)
mean(vec)
# Output
# [1] 7
# Calculate mean of Vector
vec = c(6,7,8, NA)
mean(vec, na.rm=TRUE)
# Output
# [1] 7
```

## Conclusion

In this article, you have learned how o calculate the mean or average in R with examples of DataFrame and Vector. Also learned using `na.rm=TRUE`

param to ignore the NA values.

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