How to check if the value matches the one from previous ?th row? (? is dynamic)

Question

Here is my data set. Data in

I'd like to check if the gender with "Potential Original" matched the gender with "Potential Duplicate'. There is no specified group but 1 duplicate + 1 or more original acted like a group.

Here is the output I want (for duplicate it's NA because it's comparing to itself). Data out

Appreciate your help. Thanks.

Please provide the code your tried – Rahul Agarwal Aug 29 '18 at 11:16 — Rahul Agarwal, Aug 29 '18 at 11:16

score 0 · Answer 1 · answered Aug 31 '18 at 07:46

Thanks Rahul for looking into this. This is what I tried and I think it worked. The logic is to create the seq # first for each block of Duplicate and Original and then pull the lag value with corresponding distance.

 library(data.table)
 setDT(df)[, counter := seq_len(.N), by = list(cumsum(Status == "Potential 
 Duplicate"))]

for (i in 1:nrow(df)) {
  if (df$Status[i]=="Potential Duplicate") {
   df$Gender_LAG[i] <-df2$Gender[i]
                                             } 
   else {
     df$Gender_LAG[i]<-df2$Gender[i-df2$counter[i]+1]
        }
                        }

Thanks. Looking forwards to seeing other options.

How to check if the value matches the one from previous ?th row? (? is dynamic)

1 Answers1