Subset data based on Minimum Value

Question

This might an easy one. Here\'s the data:

dat <- read.table(header=TRUE, text=\"
Seg  ID  Distance
Seg46      V21 160.37672
Seg72      V85 191.24400
Seg37         


        

Answer 1

If you prefer ddply you could do this

library(plyr)
ddply(dat, .(ID), summarize, 
      Seg = Seg[which.min(Distance)], 
      Distance = min(Distance))

#    ID    Seg  Distance
#1 V147 Seg159  14.74852
#2 V171 Seg233 193.01636
#3  V21  Seg46 160.37672
#4  V85 Seg373 167.38930