How to update existing column values in data.table?

Question

I just started this programming, apologize for asking this simple question but I am stuck.

I have a data.table called s3:

s3:

ClaimID           dx      dxgroup
15nhbfcgcda       113.8   NA
15nhbfcgcda       156.8   NA
15nhbfcgcda       110.8   059
15nhbfcfssa       135.8   NA
15nhb4dfgda       V70.3   NA
15nhbf644da       118.8   042

S3 has 30000 rows.

• I want to apply this logic:

  If dxgroup = NA(
      If dx (fisrt 4 characters match with)= (2024, 2967, 9786,9788,8263)
          then dxgroup = (first 4 character of dx)
      else dx (fisrt 3 characters match with) = (V70, 042,897)
          then dxgroup = (first 3 character of dx)
  else dxgroup = dx
  )
  

• Result should be like :

  ClaimID           dx      dxgroup
  15nhbfcgcda       113.8   113.8
  15nhbfcgcda       156.8   156.8
  15nhbfcgcda       110.8   059
  15nhbfcfssa       135.8   135.8
  15nhb4dfgda       V70.3   V70
  15nhbf644da       118.8   042
  

• Please advice ?

• I apologize: It is my first time I am asking something here, so not used to yet. So I did something like this(I have no if this is correct and I got error as well):

  sample4<-sample3[, dxgroup := { if (dxgroup == NA)

  • { if (substring(sample3$dx,1,4) == list (2501,2780,4151,5301,5751,6860,7807,7890,9898,9955,9970)) substring(sample3$dx,1,4)
  • else if (substring(sample3$dx,1,3) == list (042,493,682,850,V72)) substring(sample3$dx,1,3)
  • else if (substring(sample3$dx,1,4) == list (8540, 8541)) substring(sample3$dx,1,3)
  • else if (substring(sample3$dx,1,3) == list (043, 044)) 042
  • else if (substring(sample3$dx,1,3) == list (789) & substring(sample3$dx,1,3) != list(7891,7893,78930)) 7890
  • else if (substring(sample3$dx,1,4) == list (7865) & substring(sample3$dx,1,4) != list(78651,78652,78659)) 78650}
  • else sample3$dx}] Error in if (dxgroup == NA) { : missing value where TRUE/FALSE needed In addition: Warning message: In if (dxgroup == NA) { : the condition has length > 1 and only the first element will be used

Answer 1

You have the logic all set.

Note that with data.table (well, almost all of R), you can wrap the j in {curly brackets} and the final statement in the brackets is what will be assigned. eg:

DT[,  dxgroup :=  { if (clause1)  
                     {if (foo) beebar else bar}
                  else chewybar
                  } 
  ]