Cascading Multi-selects: Only showing unique choices

abaldenweck@blm.gov_BLM_EGIS

Kind of a follow-up to this post

I have a list describing the contents of someone's closet. I'm taking inventory of this closet while I fill out this survey, but I really only care about what colors are represented in the assemblage. So I want to know what color shirts are in the closet, regardless of what style they are.

Example table (pivoted for readability)

Item Type	Item Style	Colors possible in that Style
Shirt	Collared	Blue (Navy), Blue (Pale), Green, Red
	Henley	Blue (Pale), Grey,  White
	T-Shirt	Green, Grey, Purple, Red
	Tank-top	Black, Blue (Navy), Grey, Green, Purple

If someone selects a Collared shirt  and Tank-top, the full set of choices will appear.

Item Style	Colors possible
Collared, Tank-top	Blue (Navy), Black, Blue (Pale), Blue (Navy), Green, Grey, Red, Green, Purple

 (Survey123 puts the choices as A[0], B[0], A[1], B[1], etc...)

Since I only care about the color of his entire collection of shirts, how can I make a clean list of unique choices appear? 

Collared, Tank-top

Black, Blue (Navy), Blue (Pale), Green, Grey, Purple, Red

(If this were really what the survey was, I would cascade in reverse, starting with colors, then going to Styles, but that's not possible with my actual dataset.)

Thanks!

 

abaldenweck@blm.gov_BLM_EGIS

Okay, I have a working solution. 

The code to generate the if() statements is 

Spoiler

function choicenum(N) {
	var index_range = [];

	//Create an index range based on the count-selected in the question.
	for (var i = 1; i <= N; i++) {
		index_range.push(i);
    }
	// Create your filter statements
	var filterstr = []
	for (var y in index_range) {  
      	var midstr = []
      	midstr.push("if(count-selected(${Animal})=" + (Number(y)+1) + ", ");
      	
		// Create a sub-index for the second clause of the if()
		var subindex= []
      	for (var f = 0; f <= y; f++) {
			subindex.push(f);
   		
      		midstr.push("contains(Animal, selected-at(${Animal}, '" + f + "' )) or ")
        }
      	// Concatenates into a string, joined by a dummy character
  		var split_char= "?"
  		midstr = midstr.join(split_char);
  		// splits along the dummy character and stitches back together
  		midstr= midstr.split(split_char).join('');
  		// Removes the last "or" from the string
  		midstr = midstr.substring(0, midstr.length -4)
		
     	filterstr.push(midstr);
	}
  
	filterstr = filterstr + ", \"\"" +")".repeat(N)
	return filterstr
  
}

//Outcome for N=2
//if(count-selected(${Animal})=1, contains(Animal, selected-at(${Animal}, '0' )),
//if(count-selected(${Animal})=2, contains(Animal, selected-at(${Animal}, '0' )) 
//or contains(Animal, selected-at(${Animal}, '1' )), ""))

console.log(choicenum(2))

 It's not the ideal solution; originally I had created a script that worked dynamically. Unfortunately, S123 can't use formulas that are the result of a pulldata() or are the values in another question as filter expressions; it instead tries to filter based off the string of the expression.