Choice filters (Casacade)

Choice filters allow you to dynamically filter the options shown in a select_one or select_multiple question based on the answer to a previous question.

They are useful when you have linked dropdowns, such as showing cities based on the country selected, or filtering job titles based on department.

How choice filters work

To use a choice filter, follow these steps:

1. In the survey sheet, add a column named choice_filter.

2. In the choices sheet, add an extra column with the filtering attribute.

3. The choice_filter expression in the survey sheet must match the filter value from the selected answer.

The syntax for the filter is:

filter_column = ${question_name}

This compares a column in the choices sheet to the value selected in a previous question.

Choice filters will only work on the select_one if its defined within group that defines a page with the field-list appearance. It will not work within a group that doesnt have a field-list apperance

Example: Country and city

survey sheet

type	name	label	choice_filter
select_one country	country	Select a country
select_one city	city	Select a city	country = ${country}

choices sheet

list_name	name	label	country
country	usa	United States
country	france	France
city	nyc	New York City	usa
city	la	Los Angeles	usa
city	paris	Paris	france
city	lyon	Lyon	france

What happens:

1. The user selects a country in the first question (e.g. France).

2. The second question (Select a city) only shows cities where the country column in the choices sheet matches the selected country (france in this case).

3. So only "Paris" and "Lyon" will appear in the city dropdown.