r - How to find the nth lowest value without sorting -

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i have data set values multiple cities in each state. third (for example) lowest value in each state, , return name of city.

i can lowest value in each state with:

tapply(df2[,11],df2$state, min )

but how nth lowest (and return city name)?

data in column 11, state in column 7 (with header "state"), city name in column 2.

try example:

#dummy data df <- data.frame(   state=paste0("state",sort(rep(1:2,10))),   city=rep(paste0("city",rep(1:10,2))),   value=runif(n=20))  #get rank per state df$rank <- ave(df$value, df$state, fun = rank)  #subset 3rd lowest per state df[df$rank==3,]

edit:

as pointed out arun, partial sort solution, using data.table package:

library(data.table) dt <- data.table(df) dt[dt[, .i[value == sort(value, partial=3l)[3l]], by=state]$v1]

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