I have a field where the user inputs text Aa1Bb2Cc3

Am I able to auto populate another field by only populating the field with Bb or 3.

Auto populate the field with characters [4:6] or just [9]

How would I do this?

1 Answer 1


Yes, you should be able to do this. You can reference Survey123 Formulas

and also the Quick reference guide

The functions below should allow you auto populate another field.

Function Description Example selected(question, value)

Checks if answer is selected. Used for select_one and select_multiple questions

selected(${question_one}, 'a')


Returns the number of selected answers. Used for select_multiple questions.



Returns the length of a nonempty string.


substr(question, start, end)

Returns the substring beginning at the specified start and extends to the character at index end -1, where start and end begin at 0.

substr(${question_one},1 ,2)

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