Statistical
analysis in R is performed by using many in-built functions. Most of
these functions are part of the R base package. These functions take R
vector as an input along with the arguments and give the result.

The functions we are discussing in this chapter are mean, median and mode.

## Mean

It is calculated by taking the sum of the values and dividing with the number of values in a data series.

The function

**mean()**is used to calculate this in R.
The basic syntax for calculating mean in R is −

```
mean(x, trim = 0, na.rm = FALSE, ...)
```

Following is the description of the parameters used −

**x**is the input vector.**trim**is used to drop some observations from both end of the sorted vector.**na.rm**is used to remove the missing values from the input vector.

### EXAMPLE

```
# Create a vector.
x <- c(12,7,3,4.2,18,2,54,-21,8,-5)
# Find Mean.
result.mean <- mean(x)
print(result.mean)
```

When we execute the above code, it produces the following result −

```
[1] 8.22
```

## Applying Trim Option

When
trim parameter is supplied, the values in the vector get sorted and
then the required numbers of observations are dropped from calculating
the mean.

When trim = 0.3, 3 values from each end will be dropped from the calculations to find mean.

In
this case the sorted vector is (−21, −5, 2, 3, 4.2, 7, 8, 12, 18, 54)
and the values removed from the vector for calculating mean are
(−21,−5,2) from left and (12,18,54) from right.

```
# Create a vector.
x <- c(12,7,3,4.2,18,2,54,-21,8,-5)
# Find Mean.
result.mean <- mean(x,trim = 0.3)
print(result.mean)
```

When we execute the above code, it produces the following result −

```
[1] 5.55
```

## Applying NA Option

If there are missing values, then the mean function returns NA.

To drop the missing values from the calculation use na.rm = TRUE. which means remove the NA values.

# Create a vector. x <- c(12,7,3,4.2,18,2,54,-21,8,-5,NA) # Find mean. result.mean <- mean(x) print(result.mean) # Find mean dropping NA values. result.mean <- mean(x,na.rm = TRUE) print(result.mean)

When we execute the above code, it produces the following result −

```
[1] NA
[1] 8.22
```

## Median

The middle most value in a data series is called the median. The

**median()**function is used in R to calculate this value.## SYNTAX

The basic syntax for calculating median in R is −

```
median(x, na.rm = FALSE)
```

Following is the description of the parameters used −

**x**is the input vector.**na.rm**is used to remove the missing values from the input vector.

### EXAMPLE

```
# Create the vector.
x <- c(12,7,3,4.2,18,2,54,-21,8,-5)
# Find the median.
median.result <- median(x)
print(median.result)
```

When we execute the above code, it produces the following result −

```
[1] 5.6
```

## Mode

The
mode is the value that has highest number of occurrences in a set of
data. Unike mean and median, mode can have both numeric and character
data.

R
does not have a standard in-built function to calculate mode. So we
create a user function to calculate mode of a data set in R. This
function takes the vector as input and gives the mode value as output.

### EXAMPLE

# Create the function. getmode <- function(v) { uniqv <- unique(v) uniqv[which.max(tabulate(match(v, uniqv)))] } # Create the vector with numbers. v <- c(2,1,2,3,1,2,3,4,1,5,5,3,2,3) # Calculate the mode using the user function. result <- getmode(v) print(result) # Create the vector with characters. charv <- c("o","it","the","it","it") # Calculate the mode using the user function. result <- getmode(charv) print(result)

When we execute the above code, it produces the following result −

```
[1] 2
[1] "it"
```

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