You can use the following function types in your fields' display text or in the values of your skip or validation logic:
See here for more functions and expressions you can use.
Tip: if your calculation does not seem to work correctly, try adding white space around the operator, e.g. instead of "=($field_1+5)" use "=($field_1 + 5)"
Select functions
| Function | Description | Example |
|---|---|---|
| selected(string list, string value) | Returns true if the given value was selected from the given multi-select list, otherwise returns false. | =selected($select_symptom, "cough") |
| selected-at(string list, number index) | Returns the value of the item at the 0-based index of the given list or returns an empty string if the item does not exist (including for negative index and index 0). | =selected-at($select_symptom, 1) returns the second selected item in the list |
| count-selected(list) | Returns the number of items selected in the given list. | =count-selected($select_symptom) |
Example
Add a select many field for selecting all relevant symptoms and use the select functions above.
Use the Preview to view how it will display on the handset:
Repeat functions
| Function | Description | Example |
|---|---|---|
| repeat-index() | Returns the iteration index of the current repeating group. | See example below |
| indexed-repeat() | Indexed-repeat is a function that allows you to get information from a specific iteration of a repeat group and use in another area of the form. | =indexed-repeat($field, $group, repeat-index()) See example here. |
Example
After entering the number of household members that live in a household, a repeating group is used to capture the details of each member. The fieldworker needs to keep track of which household member they are currently capturing information for.
- In the display text type '=', then select repeat-index()
- Once the household member's name is captured you can refer to the person by name to capture their other details.
- On the device it will display as follows for the second member:
Set functions
| Function | Description | Example |
|---|---|---|
| count(list) | Returns the number of objects in the argument set | =count($repeat_group) Returns the number of repeats in a group |
| count-non-empty(list) | Returns the number of non-empty objects in the argument set. | |
| position(.. ) | Returns the current iteration within a repeating group, similar to the =repeat-index() function. | See example above |
Example
The fieldworker must make sure that they have enumerated all members of a household. Display how many members they have captured by counting the number of times they have repeated the member details group.
- The total number of household members has been captured in the $HH_Number field.
- $Member_name is a required field in the member details group.
- In the display text type '=', then select count(), then enter $Member_name as the argument.
- After editing, the function and field references will be highlighted as follows:
Geographic functions
| Function | Description | Example |
|---|---|---|
| distance(location_fields) | Returns the distance in meters, of geopoints, in the sequence provided by the points in the parameter. Note: It takes into account the circumference of the Earth around the equator and does not take altitude into account. | =distance($location1 | $location2) |
| area(location_fields) | Returns the calculated area in m2 of a set of geopoints. Note: It takes into account the circumference of the Earth around the equator but does not take altitude into account. | =area($location1 | $location2 | $location3) |
Example
Add location fields for selecting capturing coordinates and use the geographic functions above.
Use the Preview to view how it will display on the handset:
