[Solved] Calculate variable based on criteria in r

by


Plyr solution:

 library(plyr)
 ddply(df,.(ID),transform,AGE_HEAD=head(AGE,1))

OR

ddply(df,.(ID),transform,AGE_HEAD=AGE[PERNO==1])

ID AGE PERNO AGE_HEAD
1  1  30     1       30
2  1  25     2       30
3  2  25     1       25
4  2  24     2       25
5  2   3     3       25
6  3  65     1       65
7  3  55     2       65

data.table solution:

library(data.table)
DT<-data.table(df)

DT[, AGE_HEAD := AGE[PERNO==1], by="ID"]
   ID AGE PERNO AGE_HEAD
1:  1  30     1       30
2:  1  25     2       30
3:  2  25     1       25
4:  2  24     2       25
5:  2   3     3       25
6:  3  65     1       65
7:  3  55     2       65

5

solved Calculate variable based on criteria in r