Find String from One List within Another List and Return String Found

Question

I found part of what I was looking for at Matchlists/tables in power query, but I need a bit more.

Using the "Flags only" example provided at Matchlists/tables in power query, I’m comparing two lists, ListA and ListB, to check if ListB’s row content appears in ListA’s row content at all. I can’t do a one-for-one match of both rows’ contents (like with List.Intersect) because the content of a row in ListB might only be part of the content of a row in ListA.

Note that, in the query below, ListB includes “roo”, which is the first three letters in the word room. I would want to know that “roo” is in ListA’s row that has “in my room.”

The "Flags only" example provided by Matchlists/tables in power query already determines that “roo” is part of ListA’s row that has “in my room.” I built on the example to assign “yes,” instead of true when there is such a match between the ListA and ListB.

What I’d like to do is to replace “yes” with the actual value from ListB — the value “roo,” for instance. I tried to simply substitute wordB for “yes” but I got an error that wordB wasn’t recognized.

let
    ListA = {"help me rhonda",  "in my room", "good vibrations", "god only knows"},
    ListB = {"roo", "me", "only"},
    contains_word=List.Transform(ListA, (lineA)=>if List.MatchesAny(ListB, (wordB)=>Text.Contains(lineA, wordB)) = true then "yes" else "no")
in
    contains_word

The current query results in this:

    List
1   yes
2   yes
3   no
4   yes

I want the query results to be:

    List
1   roo
2   me
3   
4   only

Any idea how to make it so?

(p.s. I'm extremely new to Power Query / M)

Thanks

Answer 1

I would do this way:

let
    ListA = {"help me rhonda",  "in my room", "good vibrations", "god only knows"},
    ListB = {"roo", "me", "only"},
    contains_word=List.Transform(ListA, (lineA)=>List.Select(List.Transform(ListB, (wordB)=>if Text.Contains(lineA, wordB) = true then wordB else null), (x)=>x <> null){0}?)
in
    contains_word

[edited]

The idea is to use List.Transform twice: inner one changes list B to leave only matching values. Then 1st non-null of latest replaces string from list A (outer List.Tramsform).