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rdataframegroupingaveragecalculated-columns

How to find the average within the subgroups of columns of data frame in R programming?

trt<-c(1, 1, 2, 2, 3, 3, 1, 1, 2, 2, 3, 3, 1, 1, 2, 2, 3, 3, 1, 1, 2, 2, 3, 3, 1, 1, 2, 2, 3 ,3)
plant<-c(1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 5, 5, 5 ,5, 5, 5)
change<-c(-9, -6, -4 , 7 , 4, 11, 18,  5, 29, 10, 29, 36, 10,  9,  4, -1 ,14 ,16 , 9 , 0, -2,  6,14, 18, -6, 13, 11, -1,  7, 15)
df<-data.frame(trt,plant,change)

df

and I want the result like this-average of the change where first 2 entries are same in trt. my data has 30 rows i want 15 in result,plz help

result

Solution

  • A base R solution using aggregate

    > aggregate(change ~ ., df, mean)
   trt plant change
1    1     1   -7.5
2    2     1    1.5
3    3     1    7.5
4    1     2   11.5
5    2     2   19.5
6    3     2   32.5
7    1     3    9.5
8    2     3    1.5
9    3     3   15.0
10   1     4    4.5
11   2     4    2.0
12   3     4   16.0
13   1     5    3.5
14   2     5    5.0
15   3     5   11.0