Introducing a WHILE LOOP to a Function

[omario]

I am working with the R programming language.

I am trying to count the first time a certain pattern (e.g. ABCD) appears in a random string (e.g. AC ABCD CDBCABCDBC - answer =6 ). I wrote a function to do this:

library(stringr)

letters <- c("A", "B", "C", "D")

results <- list()
for (i in 1:100)
    
{
    
    iteration_i = i
    letters_i = paste(sample(letters, 100, replace=TRUE, prob=c(0.25, 0.25, 0.25, 0.25)),collapse="")
    position_i = str_locate(letters_i, "ADBC") 
    
    results_tmp = data.frame(iteration_i , letters_i, position_i)
    
    results[[i]] <- results_tmp
    
}

results_df <- do.call(rbind.data.frame, results)

This looks something like this now (note: I don't think this is correct - in row 5, I see ABCD at the beginning of the row, but its being recorded as NA for some reason):

  iteration_i                                                                                            letters_i start end
1           1 BACDCCCDCCCDCDDBBCBBAACACBBBBAAABDDDACAABDDABBABADCDDCDACCBBBCABCDABCDCCCDADDDBADBDCADAABDBDCDCAACCB    NA  NA
2           2 CACACCCCDCCBADACBBAADBCABBAAAAADBDDBCADCAAADADAAABDCABBAABABBCBDADCDDDDCDBADDBDCBCDDDBDCDDAACBBBBACA    20  23
3           3 CDCBDAABDDDDADBAAABBADAADBDDDBDADDCABADDDCDABBBCBCBBACBBDADABBCDCCACDBCDCDDBDBADBCDCADDADDDBDBAAABBD    79  82
4           4 ADBCDBADADBAAACAADACACACACBDDCACBDACCBDAAABDBAAAABBCCDBADADDADCBCABCBAABDCBCDCDACDCCDBADCBDDAADBCDAC     1   4
5           5 DABCDDDCCBCDABADBBBBCDBCADCBBBDCAAACACCCBCBCADBDDABBACACBDABAAACCAAAAACCCCBCBCCABABDDADBABDDDCCDDCCC    NA  NA
6           6 DDDDDBDDDDBDDDABDDADAADCABCDAABBCCCDAABDDAACBDABBBBBABBCBDADBDCCAAADACCBCDDBDCAADCBBBCACDBBADDDDCABC    NA  NA

Currently, I am only generating 100 letters and hoping that this is enough to observe the desired pattern (sometimes this doesn't happen, notice the NA's) - is there a way to add a WHILE LOOP to what I have written to keep generating letters until the desired pattern first appears?

Can someone please show me how to do this?

Thanks!

[nirgrahamuk]

@omario

str_locate(letters_i, "ADBC")

@omario

in row 5, I see ABCD at the beginning of the row, but its being recorded as NA for some reason)

you have scrambled the order of the letters of interest.
ADBC is in the code, your post talks about ABCD...

here is an implementation with while loop

library(stringr)

letters <- c("A", "B", "C", "D")

results <- list()
found <- FALSE
while(!found)
{
  letters_i = paste(sample(letters, 100, replace=TRUE, prob=c(0.25, 0.25, 0.25, 0.25)),collapse="")
  position_i = str_locate(letters_i, "ABCD") 
  found<-!any(is.na(position_i))
  results_tmp = data.frame( letters_i, position_i)
  results <- rbind(results,results_tmp)
}