Increment Number By Value With Condition - Array Formula

Question

i'm confused with the following condition, simply i want to have arrayformula or maybe a custom-formula to increment number in a way bound by specific condition based on value in other column, put it simply:

if the group doesn't change and sub-group is different increment number by 1
else if the group doesn't change and sub-group is doesn't change (same) hold value by previous
else if the group change regardless sub-group value reset number back to 1

for ilustration

** notes Number is the result that i want, in example i fill it manually

Group	Sub-Group	Animal	Number
Land	poisonus	snake	1
land	friendly	dog	2
land	friendly	cat	2
land	scary	lion	3
aquatic	friendly	nemo fish	1
aquatic	predator	shark	2

UPDATE (dummy file link):
https://docs.google.com/spreadsheets/d/1DAPf-DvWz50_DJ0IqAoSHbfEnfg_mN1lNXHcCjkj27M/edit#gid=0

Answer 1

I have entered my solution in cell D1 of the sheet "Erik Help." As I said in the comments to your original post, this is a more complex solution than I can generally offer here on the free, volunteer-run forums. I did choose to develop and share the formula with you, but I will need to leave it to you (and any other future site visitors who may be interested) to study the formula for understanding how it works. Explaining the formula would take longer than writing it.

Here is the formula:

=ArrayFormula({"Number"; IF(A2:A="",,VLOOKUP(LOWER(A2:A&B2:B),QUERY({UNIQUE(FILTER({A2:B,A2:A&B2:B},A2:A<>"")),COUNTIFS(QUERY(UNIQUE(FILTER({A2:B,A2:A&B2:B},A2:A<>"")),"Select Col1"),QUERY(UNIQUE(FILTER({A2:B,A2:A&B2:B},A2:A<>"")),"Select Col1"),SEQUENCE(COUNTA(QUERY(UNIQUE(FILTER({A2:B,A2:A&B2:B},A2:A<>"")),"Select Col1"))),"<="&SEQUENCE(COUNTA(QUERY(UNIQUE(FILTER({A2:B,A2:A&B2:B},A2:A<>"")),"Select Col1"))))},"Select Col3, Col4"),2,FALSE))})

Answer 2

try:

=INDEX(IF(A4:A="",,VLOOKUP(A4:A&B4:B, {UNIQUE(A4:A&B4:B), COUNTIFS(
 REGEXEXTRACT(UNIQUE(A4:A&"×"&B4:B), "(.*)×"), 
 REGEXEXTRACT(UNIQUE(A4:A&"×"&B4:B), "(.*)×"), 
 SEQUENCE(COUNTA(UNIQUE(A4:A&"×"&B4:B))), "<="&
 SEQUENCE(COUNTA(UNIQUE(A4:A&"×"&B4:B))))}, 2, 0)))