R Language Aggregating data frames Aggregating with base R
Example
For this, we will use the function aggregate, which can be used as follows:
aggregate(formula,function,data)
The following code shows various ways of using the aggregate function.
CODE:
df = data.frame(group=c("Group 1","Group 1","Group 2","Group 2","Group 2"), subgroup = c("A","A","A","A","B"),value = c(2,2.5,1,2,1.5))
# sum, grouping by one column
aggregate(value~group, FUN=sum, data=df)
# mean, grouping by one column
aggregate(value~group, FUN=mean, data=df)
# sum, grouping by multiple columns
aggregate(value~group+subgroup,FUN=sum,data=df)
# custom function, grouping by one column
# in this example we want the sum of all values larger than 2 per group.
aggregate(value~group, FUN=function(x) sum(x[x>2]), data=df)
OUTPUT:
> df = data.frame(group=c("Group 1","Group 1","Group 2","Group 2","Group 2"), subgroup = c("A","A","A","A","B"),value = c(2,2.5,1,2,1.5))
> print(df)
group subgroup value
1 Group 1 A 2.0
2 Group 1 A 2.5
3 Group 2 A 1.0
4 Group 2 A 2.0
5 Group 2 B 1.5
>
> # sum, grouping by one column
> aggregate(value~group, FUN=sum, data=df)
group value
1 Group 1 4.5
2 Group 2 4.5
>
> # mean, grouping by one column
> aggregate(value~group, FUN=mean, data=df)
group value
1 Group 1 2.25
2 Group 2 1.50
>
> # sum, grouping by multiple columns
> aggregate(value~group+subgroup,FUN=sum,data=df)
group subgroup value
1 Group 1 A 4.5
2 Group 2 A 3.0
3 Group 2 B 1.5
>
> # custom function, grouping by one column
> # in this example we want the sum of all values larger than 2 per group.
> aggregate(value~group, FUN=function(x) sum(x[x>2]), data=df)
group value
1 Group 1 2.5
2 Group 2 0.0
