| layout | post |
|---|---|
| title | How do I use the count-selected() function? |
| permalink | /faq/using-count-selected-function |
| category | faq |
The count-selected function is used with select_multiple questions. It will count the number of answer choices selected in the select_multiple question and return that value as an integer. See the example below:
| survey | ||||
|---|---|---|---|---|
| type | name | label | calculation | |
| select_multiple cities | cities_visited | Select all of the cities you have visited. | ||
| calculate | num_cities_visited | count-selected(${cities_visited}) |
A much more practical application of count-selected is to restrict a user from selecting certain answer choices together. Take the following question as an example:
In this question, one of the options is No risk symptoms observed. It wouldn’t make any sense for a user to select other risk symptoms and then also select No risk symptoms observed. Using the count-selected function, you can restrict the user from selecting No risk symptoms observed with any other answer choice. See the XLSForm snippet below:
| survey | ||||
|---|---|---|---|---|
| type | name | label | constraint | |
| select_multiple risks | risks_observed | Does the woman have any risk symptoms? | (selected(., 'none') and (count-selected(.) = 1)) or not(selected(., 'none')) | |
| choices | ||||
| list name | name | label | ||
| risks | pallor | Pallor | ||
| risks | swelling | Swelling / Edema | ||
| risks | bleeding | Bleeding | ||
| risks | jaundice | Jaundice | ||
| risks | convulsions | Fits / Convulsions | ||
| risks | none | No risk symptoms observed | ||
| risks | others | Others |
The constraint logic is specifying that if the user selects the answer choice name none, then only this answer can be selected (count-selected(.) = 1), or answer choice name none is not selected at all.