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Asked: 2026-06-11T18:18:22+00:00

Using R, I would like to create a new column (MaxAct) showing the maximum

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Using R, I would like to create a new column (MaxAct) showing the maximum numbers of a different column (ActNo) while grouping by two factors (HHID and PERID)

For example, I have this data set:

UID HHID PERID ActNo
1   1000 1     1
2   1000 1     2
3   1000 1     3
4   1000 2     1
5   1000 2     2
6   2000 1     1
7   2000 1     2
8   2000 1     3
9   2000 1     4
10  2000 2     1
11  2000 2     2

Then I want to add the new column (MaxAct) as follows:

UID HHID PERID ActNo MaxAct
1   1000 1     1     3
2   1000 1     2     3
3   1000 1     3     3
4   1000 2     1     2
5   1000 2     2     2
6   2000 1     1     4
7   2000 1     2     4
8   2000 1     3     4
9   2000 1     4     4
10  2000 2     1     2
11  2000 2     2     2
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1 Answer

  1. Editorial Team
    dat$MaxAct <- with(dat, ave(ActNo, HHID, PERID, FUN=max) )

    For problems involving single vectors and grouping where you want the length of the result to equal the row count, ave is your function of choice. For more complicated problems, the lapply(split(dat, fac), FUN) approach may be needed or use do.call(rbind, by( ...))

    If you have missing values:

    dat$MaxAct <- with(dat, ave(ActNo, HHID, PERID, FUN=function(x) max(x, na.rm=TRUE) )  )
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