XLSForm Select Multiple Skip Logic with selected()

To show a question when an option of a select_multiple question was ticked, write selected(${question}, 'choice_name') in its relevant column, for example selected(${water_sources}, '4'). A plain ${water_sources} = '4' looks right but only works when that one option is ticked alone. ODK, KoboToolbox and SurveyCTO all read selected() the same way, and every example below compiles with pyxform and ODK Validate, the check ODK Central runs when you upload a form.

Download example form (.xlsx)All six examples in one XLSForm, one group each. Tested with pyxform and ODK Validate; free to reuse under CC BY 4.0.Download

Why does = not work on a select_multiple question?

A select_multiple answer is stored as one text value: the names of every ticked option, separated by spaces. A household that uses piped water and a river is saved as 1 4. So ${water_sources} = '4' asks "is the whole answer exactly 4?", which is false as soon as a second option is ticked. The form compiles and gives no error; the follow-up just never appears for most respondents.

This is the most common select_multiple question on the ODK and KoboToolbox forums. A typical case: an "Other" follow-up with ${qst} = '99' that works on a select_one and stops working when the question is changed to select_multiple.

selected() checks whether one name is in the list, whatever else was ticked:

type	name	label	relevant
select_multiple water_source	water_sources	Which water sources does the household use?
integer	river_distance	How many minutes does it take to walk to the river or pond?	selected(${water_sources}, '4')

◀ ▶surveychoicessettings+

list_name	name	label
water_source	1	Piped water
water_source	2	Protected well
water_source	3	Unprotected well
water_source	4	Surface water (river or pond)
water_source	-96	Other

◀ ▶surveychoicessettings+

Three rules cover most mistakes:

• Lowercase selected. Function names are case-sensitive, so Selected( fails.
• Two arguments. The question reference first, then one choice name.
• The choice name in quotes. Use '4', not 4 and not the label "Surface water".

How do I show a question when any of several options is ticked?

Join one selected() per option with or. Here a care-seeking question appears when the child had fever, cough or diarrhoea, but not when the only symptom was a rash:

type	name	label	relevant
select_multiple symptom	symptoms	Which symptoms did the child have in the last two weeks?
select_one yes_no	sought_care	Did you seek advice or treatment for the illness?	selected(${symptoms}, '1') or selected(${symptoms}, '2') or selected(${symptoms}, '3')

◀ ▶surveychoicessettings+

list_name	name	label
symptom	1	Fever
symptom	2	Cough
symptom	3	Diarrhoea
symptom	4	Skin rash
symptom	-96	Other
yes_no	1	Yes
yes_no	0	No

◀ ▶surveychoicessettings+

Each selected() takes one name only. selected(${symptoms}, '1' or '2') is a common shortcut, and it fails.

How do I show a question only when two options are both ticked?

Use and instead of or. This asks about crop-livestock integration only for households that earn from both crop farming and livestock:

type	name	label	relevant
select_multiple income_source	income_sources	What were the household's sources of income in the last 12 months?
select_one yes_no	uses_manure	Does the household use livestock manure on its crops?	selected(${income_sources}, '1') and selected(${income_sources}, '2')

◀ ▶surveychoicessettings+

list_name	name	label
income_source	1	Crop farming
income_source	2	Livestock
income_source	3	Wage labour
income_source	4	Petty trade
income_source	5	Remittances

◀ ▶surveychoicessettings+

and and or are lowercase operators in XLSForm, not Excel functions. When you mix them, add parentheses so the form reads the way you mean it.

How do I show a question when an option was NOT selected?

Wrap selected() in not(). A KoboToolbox forum user wanted a follow-up to appear when apple or banana was ticked, but never when grapes or orange were ticked as well. The same pattern in a WASH survey: ask about water storage only when the household uses an improved source (1 or 2) and no unimproved one (3 or 4):

type	name	label	relevant
select_multiple water_source	water_sources	Which water sources does the household use?
select_one yes_no	covered_storage	Is drinking water stored in a covered container?	(selected(${water_sources}, '1') or selected(${water_sources}, '2')) and not(selected(${water_sources}, '3')) and not(selected(${water_sources}, '4'))

◀ ▶surveychoicessettings+

The parentheses around the or part matter. Without them, and binds first and a household with piped water and a river would still see the question.

not is a function, so it needs its own brackets: not(selected(...)). Writing not selected(...) is rejected.

How do I show a question based on how many options were ticked?

Use count-selected(), which returns the number of ticked options. Asking for the main source of income only makes sense when there is more than one:

type	name	label	relevant
select_multiple income_source	income_sources	What were the household's sources of income in the last 12 months?
select_one income_source	main_income	Which of these was the main source of income?	count-selected(${income_sources}) >= 2

◀ ▶surveychoicessettings+

Use count-selected(${q}) = 1 for "exactly one option", and count-selected(${q}) >= 1 for "at least one option". The same function in a constraint column limits how many options can be ticked; the XLSForm constraint examples cover that.

How do I ask follow-up questions for each selected option?

Give each option its own group and put selected() on the begin group row. Every question inside inherits the condition, so you write it once per option instead of once per question:

type	name	label	relevant
select_multiple income_source	income_sources	What were the household's sources of income in the last 12 months?
begin group	livestock_block	Livestock income	selected(${income_sources}, '2')
integer	cattle_count	How many cattle does the household own?
integer	livestock_income	How much did the household earn from livestock in the last month?
end group	livestock_block
begin group	wage_block	Wage labour income	selected(${income_sources}, '3')
integer	wage_days	How many days of paid work did household members do in the last month?
integer	wage_income	How much did the household earn from wage labour in the last month?
end group	wage_block

◀ ▶surveychoicessettings+

This is the same group pattern as in skip logic in XLSForm, with selected() instead of =. If you need the same set of questions for every ticked option, a repeat group is less work than one group per option.

Common select_multiple skip logic errors and how to fix them

These are the messages ODK Validate and pyxform return, which is what you see when ODK Central, KoboToolbox or the XLSForm converter rejects a form:

You wrote	Write instead	Error you will see
${q} = '4'	selected(${q}, '4')	No error, but the question only shows when 4 is ticked alone
contains(${q}, '1')	selected(${q}, '1')	No error, but codes 10, 11 and 12 also match
Selected(${q}, '4')	selected(${q}, '4')	cannot handle function 'Selected'
selected(${q})	selected(${q}, '4')	Requires 2 arguments but 1 provided
selected(${q}, 4)	selected(${q}, '4')	The second parameter to the selected() function must be in quotes (like '1').
selected(${q}, '3' or '4')	selected(${q}, '3') or selected(${q}, '4')	The second parameter to the selected() function must be in quotes (like '1').
not selected(${q}, '4')	not(selected(${q}, '4'))	Couldn't understand the expression starting at this point
selected(...) AND selected(...)	selected(...) and selected(...)	Couldn't understand the expression starting at this point
${source} (typo in the name)	${sources}	Could not find the name 'source'.

The first two rows are the dangerous ones: the form compiles and the logic is silently wrong for part of your sample. Test them in preview by ticking two options at once. For other messages, see common XLSForm errors, or paste your form into the free XLSForm validator.

Does this work the same in ODK, KoboToolbox and SurveyCTO?

Yes. All three use the ODK functions selected(), not() and count-selected(), with the same arguments. What differs is where you type the condition:

Platform	Where the condition goes
ODK (XLSForm)	relevant column of the follow-up question or group
KoboToolbox Formbuilder	Question Settings, then Skip Logic: use the condition builder, or choose to enter the logic in XLSForm code and type the selected() expression
KoboToolbox (XLSForm upload)	Same as ODK
SurveyCTO	Column named relevance instead of relevant; the expression is the same

selected() also works on select_one questions, so you can use it everywhere and switch a question between select_one and select_multiple without rewriting its skip logic. The if statement guide shows the same function inside calculations.

Why select_multiple logic deserves a test with two ticks

Most people test a follow-up by ticking the one option it depends on, and that test passes even with =. The bug only shows when a real respondent ticks two options, which on questions about income sources, symptoms or water sources is most of them. A form that skips a follow-up for those households leaves a hole you only find at analysis, when you can no longer go back and ask.

Build my first form free

Next: Skip logic in XLSForm →