Extract last sequence of numerical value from string

[MichaelJSchulz]

I have a process that works but it is rather inelegant. I'm sure there must be a better way to do this.

In a certain column, the last several characters might be numbers. If the length of a number sequence is four, five, or six characters then I need to extract that sequence into a new column. If the length of final sequence numbers is less than four characters, then nothing should be extracted. There may be numbers at the beginning of the string and/or in the middle but only the numerical characters at the end of the string are of interest.

There is not a constant delimiter. There may or may not be a space between the last alpha character and the first numerical character. There might or might not be a symbol chacacter, such as a colon or a dash.

ColumnA                                     NewColumn

TEXT TEXT TEXT 123456             123456

TEXT TEXT TEXT TEXT 1234        1234

TEXT TEXT TEXT12345                 12345

TEXT 123 TEXT TEXT-123456       123456

1234 TEXT TEXT TEXT:12345        12345

TEXT TEXT TEXT TEXT 123            null

1234 TEXT TEXT TEXT 1                null

TEXT TEXT 123456 TEXT               null

[Vijay_A_Verma · Accepted solution]

You may use below in a custom column

= if Text.Select(Text.End([ColumnA],6),{"0".."9"})=Text.End([ColumnA],6) then Text.End([ColumnA],6) 
else if Text.Select(Text.End([ColumnA],5),{"0".."9"})=Text.End([ColumnA],5) then Text.End([ColumnA],5)
else if Text.Select(Text.End([ColumnA],4),{"0".."9"})=Text.End([ColumnA],4) then Text.End([ColumnA],4)
else null

EDIT - Another alternative construct is this which is more flexible

=[a=List.LastN(List.Transform(Text.ToList([ColumnA]),(x)=>if Text.Contains(Text.Combine({"0".."9"}),x) then x else null), each _ <> null),
b=if List.Count(a)<4 then null else Text.Combine(a)][b]

[MichaelJSchulz]

That's fantastic. Thank you!

I understand how the first approach works but I'm having trouble wrapping my mind around the second approach.

Would you explain how it works?