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aggregate and count unique values in R

I have a data set of Vehicle types as factors (11,12,13=type of cars) for each Vehicle type I have a number of Unit Id (=specific cars) I want to count how many uniqe UnitId I have in each vehicle Type. i tried: aggregate(UnitId~VehicleType, test, unique)->res1

Solution

  • For the updated question, i.e. "is there a way to find out if a UnitId appers in more then one VehicleType"

     with(test, names(rowSums(!!table(UnitId, VehicleType))>1))

    Copy/pasting from the comments based on your original question ("counting unique values by group")

    aggregate(UnitId~VehicleType, test, function(x) length(unique(x)))

    Or

    with(test, colSums(!!table(UnitId, VehicleType)))

    Or

    library(data.table)
setDT(test)[, length(unique(UnitId)), VehicleType]

    data

    set.seed(24)
test <- data.frame(VehicleType=sample(11:18,60, replace=TRUE), 
  UnitId=sample(1:10, 60, replace=TRUE))