Median function in R – median()

Median function in R – median() calculates the sample median. The median is the value at the middle when the data is sorted in ascending order. Median of a group can also calculated using median() function in R by providing it inside the aggregate function. with median() function we can also find row wise median using dplyr package and also column wise median lets see an example of each.

  • Median of the list of vector elements with NA values
  • Median of a particular column of the dataframe in R
  • column wise median of the dataframe using median() function
  • Median of the group in R dataframe using aggregate() and dplyr package
  • Row wise median of the dataframe in R using median() function

 

Syntax for median function in R:

median(x, na.rm = FALSE, …)
  • x – numeric vector
  • rm- whether NA should be removed, if not, NA will be returned

 

Example of Median function in R with odd observation:

# R median function with 7(odd) observation

x <-c(1.234,2.342,3.4,-4.562,5.671,12.345,-14.567)
median(x)

There are 7 observations in above examples. When arranged in ascending order 4th value is the median value so the output will be

output:
[1] 2.342

 

Example of Median function in R with even observation:

# R median function with 6(even) observation

x <-c(1.234,2.342,-4.562,5.671,12.345,-14.567)
median(x)

There are 6 observations in above example. So the median will be average of 3rd and 4th value when arranged in ascending order. So the output will be (1.234+2.342)/2

output:
[1] 1.788

 

Example of Median function with NA:

Median function doesn’t give desired output, If NAs are present in the vector. so it has to be handled by using na.rm=TRUE in median() function

# R median function for input vector which has NA.

x <-c(1.234,2.342,-4.562,5.671,12.345,-14.567,NA)
median(x,na.rm=TRUE)
output:
[1] 1.788

 

 

Example of median() function in R dataframe: 

Lets create the data frame to demonstrate median function – median() in r

### create the dataframe 
my_basket = data.frame(ITEM_GROUP = c("Fruit","Fruit","Fruit","Fruit","Fruit","Vegetable","Vegetable","Vegetable","Vegetable","Dairy","Dairy","Dairy","Dairy","Dairy"), 
                       ITEM_NAME = c("Apple","Banana","Orange","Mango","Papaya","Carrot","Potato","Brinjal","Raddish","Milk","Curd","Cheese","Milk","Paneer"),
                       Price = c(100,80,80,90,65,70,60,70,25,60,40,35,50,120),
                       MRP = c(101,85,85,96,67,73,65,71,33,64,45,36,54,123))
my_basket

so the resultant dataframe will be

Median function in R 11

 

 

Median of a column in R data frame using median() function :

Median() function in R 22

median() function takes the column name as argument and finds the median of that particular column

# median() function in R : median of a column in data frame

median(my_basket$Price)

so the resultant median of “Price” column will be

output:

[1] 67.5

column wise median using median() function:

median() function is applied to the required column through mapply() function, so that it  calculates the meidan of required column as shown below.

 
# median() function in R : median of multiple column in data frame 

 mapply(median,my_basket[,c(-1,-2)])

so the resultant median of “Price” and “MRP” columns will be

Median function in R 12

 

Median of the column by group using median() function

aggregate() function along with the median() function calculates the median of a group. here median of “Price” column, for “Item_Group” is calculated.

##### Median of the column by group 
aggregate(x= my_basket$Price,
          by= list(my_basket$ITEM_GROUP),
          FUN=median)

Item_group has three groups “Dairy”,”Fruit” & “Vegetable”. median of price for each group is calculated as shown below

Median function in R 13

 

median of the column by group  and populate it by using median() function:

group_by() function along with the median() function calculates the median of a group. here median of “Price” column, for “Item_Group” is calculated and populated across as shown below

#### median of the column by group and populate it using dplyr

library(dplyr)

my_basket %>%
  group_by(ITEM_GROUP) %>%
  mutate(median_by_group = median(Price))

Item_group has three groups “Dairy”,”Fruit” & “Vegetable”. median of price for each group is calculated and populated as shown below

Median function in R 14

 

Row wise median using median() function along with dplyr

Row wise median is calculated with the help rowwise() function of dplyr package  and median() function as shown below

## row wise median using dplyr 
library(dplyr)

my_basket %>%
  rowwise() %>%
  mutate(
    Median_price = median(c(Price,MRP))
  )

row wise median of “Price” and “MRP” is calculated and  populated for each row as shown below

Median function in R 15

 

For further understanding of median() function in R using dplyr one can refer the dplyr documentation


Related Topics:

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