Dear kind people of the internet, I need help. I am trying to split a string column into several columns and keep the null/NA entries.

```
df <- cSplit(df, "question", "_")

```

This code currently splits them but removes the null entries and shows the following warming message:

```
Warning messages:
1: In type.convert.default(X[[i]], ...) :
  'as.is' should be specified by the caller; using TRUE

```

df

```
client_id   question
15962       eng_child_pregnancy_standard_focused
15963       null
15964       xho_child_developed_sleep
15965       eng_mother_spacing_other
15966       null
15967       null

```

Current split df using the above code:

```
client_id   question       question_2      question_3      question_4     question_5
15962       eng            child           pregnancy       standard      focused
15964       xho            child           developed       sleep         NA
15965       eng            mother          spacing         other         NA

```

How do I keep the null entries and what does the warning mean?