Hello,
I am trying to create a function that will move through each record of  a data frame, find the value in the "HUC" column, then
randomly select another observation from the dataframe with the same value in "HUC" column, as well as the same value in "Yr" column as the first observation. I want the function to produce a list of the RchID of the first observation, the RchID of the second randomly chosen observation, and several other characteristics of the randomly chosen observation.  Below is the code I have written, but it doesn't work.

Thanks for any help.
Christy


################test
roads=read.csv("streamland23.csv")

for (i in 1:nrow (roads)){
Sitetype= roads$Sitetype
yr=roads$REACH_Yr
initRchid=roads$RchID
huc1=roads$HUC

sample.df <- function(df, n) df[sample(nrow(df), n), , drop = FALSE]

selected=sample.df(roads[roads$HUC == "huc1"& roads$REACH_Yr =="yr" , ], 1)


output=cbind (initRchid,selected$RchID,selected$Sitetype,selected$REACH_Yr)

}




Christy Meredith
USDA Forest Service
Rocky Mountain Research Station
PIBO Monitoring
Data Analyst
Voice: 435-755-3573
Fax: 435-755-3563





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