Extract row corresponding to minimum value of a variable by group

Question

I wish to (1) group data by one variable (State), (2) within each group find the row of minimum value of another variable (Employees), and (3) extr

Answer 1

Slightly more elegant:

library(data.table)
DT[ , .SD[which.min(Employees)], by = State]

   State Company Employees
1:    AK       D        24
2:    RI       E        19

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Slighly less elegant than using .SD, but a bit faster (for data with many groups):

DT[DT[ , .I[which.min(Employees)], by = State]$V1]

Also, just replace the expression which.min(Employees) with Employees == min(Employees), if your data set has multiple identical min values and you'd like to subset all of them.

See also Subset rows corresponding to max value by group using data.table.