R Check for levels within a group and duplicate row if not present

Question

I have a problem with in Shiny which I will show in a simple example:

I have the following data:

Group<-c("A","A","B","C","C","D")
Value<-c(1,2,6,7,3,9)

df<-data.frame(Group, Value)

  Group Value 
     A     1   
     A     2   
     B     6   
     C     7   
     C     3   
     D     9

Then I add a row to see how many reps a group has:

df$num <- ave(df$Value, df$Group,  FUN = seq_along)

  Group Value num
     A     1   1
     A     2   2
     B     6   1
     C     7   1
     C     3   2
     D     9   1

Now, I would like it, to check if the group contains a 2nd rep, and if not, duplicate the 1st row of the group (containing num=1) and setting num to 2. So I would like to end up with:

  Group Value num
     A     1   1
     A     2   2
     B     6   1
     B     6   2 #this row is added
     C     7   1
     C     3   2
     D     9   1
     D     9   2 #this row is added

I have tried to search for solution, but I mainly ended up with subject like a condition that is based on a certain value, rather than conditions within a group.

Could someone help me? I would appreciate it a lot!

score 0 · Accepted Answer · answered Oct 25 '18 at 14:01

0

Can this code do the trick ?

res <- lapply(unique(df$Group), function(x){
  a <- df[df$Group == x, ]
  if(nrow(a) == 1) {
    a <- a[rep(row.names(a), 2), ]
    a$num <- c(1:2)
  }
  a
})
do.call(rbind, res)

answered Oct 25 '18 at 14:01

Bambs

443
4
14

Yes! Thank you! I just came across an extra problem, I tried to change your answer but I can't.... what if this is my dataset: – Lotw Oct 26 '18 at 06:13
Sorry, again: @Pauline Thank you! This works perfectly :) I just ran into a new problem, would you know how it works when I have the following data: Group1 – Lotw Oct 26 '18 at 06:24
1

There is probably a simplier way to do this but I think this works : res – Bambs Oct 26 '18 at 08:50

R Check for levels within a group and duplicate row if not present

1 Answers1