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How to find the groupwise mean and save it in a data frame object in R?
We often need groupwise mean in data analysis, especially in situations where analysis of variance techniques is used because these techniques helps us to compare different groups based on their measures of central tendencies and measures of variations. It can be done by using aggregate function so that the output can be saved in a data frame object. In the below examples, we can see how it can be done and also check the final object type.
Example
Consider the below data frame −
set.seed(109)
Salary<-sample(10000:20000,20)
Group<-sample(c("High-school","Graduate","Post-Graduate"),20,replace=TRUE)
df1<-data.frame(Group,Salary)
df1Output
Group Salary 1 Graduate 10250 2 High-school 14923 3 High-school 18928 4 High-school 19800 5 Graduate 15974 6 High-school 16270 7 Post-Graduate 19832 8 Graduate 19246 9 Graduate 11699 10 Graduate 17424 11 High-school 14875 12 Post-Graduate 12319 13 Post-Graduate 16900 14 High-school 12361 15 Post-Graduate 15809 16 Post-Graduate 19854 17 High-school 14387 18 High-school 13647 19 Graduate 18587 20 Graduate 11817
Finding the groupwise mean with aggregate function −
Groupwise_mean<-aggregate(df1$Salary,list(df1$Group),mean) Groupwise_mean Group.1 x 1 Graduate 14924.60 2 High-school 16524.57 3 Post-Graduate 17362.67
Checking whether the object Groupwise mean is a data frame or not −
is.data.frame(Groupwise_mean) [1] TRUE
Let’s have a look at another example −
Example
Class<-rep(LETTERS[1:4],times=5) Age<-sample(19:30,20,replace=TRUE) df2<-data.frame(Class,Age) df2
Output
Class Age 1 A 29 2 B 22 3 C 26 4 D 20 5 A 28 6 B 21 7 C 19 8 D 24 9 A 29 10 B 30 11 C 23 12 D 25 13 A 21 14 B 21 15 C 21 16 D 20 17 A 21 18 B 24 19 C 19 20 D 21
> Groupwise_mean_Age<-aggregate(df2$Age,list(df2$Class),mean)
> Groupwise_mean_Age
Group.1 x
Group.1x 1 A 24.8 2 B 25.2 3 C 25.2 4 D 24.0 > is.data.frame(Groupwise_mean_Age) [1] TRUE
Updated on: 07-Oct-2020
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