Comparing Two Lists/ Variables

Question

Question

Is there a way to compare the content of two variables/ lists and if they share a common element/ value return 1?

Example the two below both have "Yellow":

Set y = "Red, Green, Orange, Yellow"

Set x = "Purple, Black, Yellow, Pink"

The lists I am working with have over 30 elements/values that vary so it is difficult to hard code it to say look for "Yellow".

Product version: IRIS 2022.1

Discussion (12)3

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David Hockenbroch · Mar 22

If you want to treat them as lists, you probably want to use $LISTFROMSTRING along with $LISTGET, $LISTFIND, and $LISTLENGTH. All of which can be abbreviated to their initials, by the way - $LFS, $LG, $LF, $LL.

set y = $LFS("Red,Green,Orange,Yellow")
set x = $LFS("Purple,Black,Yellow,Pink")
for i=1:1:$LL(x){
    if $LF(y,$LG(x,i)) > 0 { 
        write $LG(x,i)_" found in both lists!",!
        //Or whatever else you want to do when you find a match here . . .
    }
}

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Robert Cemper · Mar 22

eventually better to check for longer lists

USER>s x=$lfs("Purple,Black,Yellow,Pink")
USER>s y=$lfs("Red,Green,Orange,Yellow")
USER>f z="y","x" f i=1:1:$ll(@z) i $i(dif($li(@z,i)))
 
USER>zw dif
dif("Black")=1
dif("Green")=1
dif("Orange")=1
dif("Pink")=1
dif("Purple")=1
dif("Red")=1
dif("Yellow")=2

looping with $o() over dif() allows programmatic check

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Herman Slagman · Mar 22

 Set x="Purple,Black,Yellow,Pink,Yellow,White,White,a,b,c,d,e,f"
Set y="Red,Green,Orange,Yellow,z,y,x,w,v"
Set Found=0
For i=1:1:$Length(x,",") {
  For i2=1:1:$Length(y,",") {
    If $Piece(x,",",i)=$Piece(y,",",i2) {
      Write $Piece(x,",",i)," = ",$Piece(y,",",i2),!
      Set Found=i_","_i2
      Return Found
     }
  }
}

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Julius Kavay · Mar 25

You can edit (or enhance) the above code to give you all matching elements. Below I share a code with you where you can choose the result data type (%List or %String) and the result scope (all the matching elements or just the first match).

/// Find common items of two lists or in two delimited strings
/// (as used in a $piece-function)
/// 
/// itm1: first list (as %List or comma-delimited %String)
/// itm2: other list (as %List or comma-delimited %String)
/// ans : 0 = return a comma-delimited %String with the first match found
///       1 = return a comma-delimited %String with all matches found
///       2 = return a %List with the first match found
///       3 = return a %List with all matches found
///       
/// return value: according to <ans> argument
///       
/// Hint: the "$d(var)," part is only needed if the <itm1> argument is
///       of %List type and can contain an "undefined" element like the
///       second element in $lb(11,,33).
///       
ClassMethod FindCommonItems(itm1, itm2, ans = 0)
{
    set ptr=0, res="", all=ans#2
    set:'$lv(itm1) itm1=$lfs(itm1) set:'$lv(itm2) itm2=$lfs(itm2)
    
    while $listnext(itm1,ptr,val) { if $d(val),$lf(itm2,val) { set res=res_$lb(val) quit:'all } }
    quit $s(ans<2:$lts(res), 1:res)
}

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score 0 · Answer 1 · 2024-03-22T16:01:50-04:00

Christine Nyamu · Mar 22

Thank you @David Hockenbroch , I will try this out

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score 0 · Answer 2 · 2024-03-25T08:59:24-04:00

Christine Nyamu · Mar 25

Thank you @Robert Cemper

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score 1 · Answer 3 · 2024-03-26T08:48:57-04:00

This one will incorrectly flag an entry being in both lists if it appears twice in 1 list. That may not be possible due to constrants elsewhere, but it's something to be careful about

score 0 · Answer 4 · 2024-03-25T08:59:08-04:00

@Herman Slagman this worked. However, when I had more than one repeating values e.g.

Set x="Purple,Black,Yellow,Pink,Orange,White,a,b,c,d,e,f"
Set y="Red,Green,Orange,Yellow,z,y,x,w,v"

It only returned that Yellow was found in both lists and ignored the Orange. I probably just need to edit the code that you shared. Thank you!

score 0 · Answer 5 · 2024-03-26T09:53:22-04:00

Christine Nyamu · Mar 26

Thank you Julius

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score 1 · Answer 6 · 2024-03-26T07:20:52-04:00

You are right, but this was based on your original question: "if they share a common element/ value return 1"

But the code is easily enhanced to return all common values.

score 0 · Answer 7 · 2024-03-26T08:31:46-04:00

I haven't put a massive amount of thought into this so it might be garbage for time/space complexity....

Set y = "Red, Green, Orange, Yellow"
Set x = "Purple, Black, Yellow, Pink"
set x=$ZSTRIP(x,"*W")
set y=$ZSTRIP(y,"*W")
k ^||members
for i=1:1:$L(x,","){
    set ^||Members($P(x,",",i),1)=""
}

for j=1:1:$L(y,","){
    set ^||Members($P(y,",",j),2)=""
}

//Now do a quick traverse of our members
set key=""
set both=""
for   {
    set key=$O(^||Members(key))
    quit:key=""
    set key2=""
    set key2=$O(^||Members(key,key2))
    if ($O(^||Members(key,key2))'="" set both=both_key_","
}

w !,"These records are in both lists "_both

score 0 · Answer 8 · 2024-03-26T09:50:33-04:00

Christine Nyamu · Mar 26

Thanks Chris

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