aggregate function in R Splits the data into subsets, computes summary statistics for each, and returns the result in a convenient form.

aggregate_example.R

# how to use aggregate function in R
#say I have a data frame where I keep track how much gas I paid for each time to the pump
read.csv("gas.csv",header=T)
head(gas)
#  amount month
#1  36.21   Jun
#2  30.22   Jun
#3  35.42   Jul
#4  34.12   Jul
#5  36.09   Aug
#6  35.29  Sept

#we can aggregate numbers for each month
#each call to aggregate returns a dataframe

#total amount for each month
aggregate(gas["amount"], by=gas[c("month")],FUN=sum)

#  month   amount
#1   Aug 36.09000
#2   Dec 32.14667
#3   Jul 34.77000
#4   Jun 33.21500
#5   Nov 28.57667
#6   Oct 35.20000
#7  Sept 35.27000

#average amount paid each trip in each month
aggregate(gas["amount"], by=gas[c("month")],FUN=mean)