Using arrayformula with countif only up to a certain row - google-sheets

Question

I have a sheet with a column of data where the entry is one of two strings, for simplicity's sake we'll say "A" and "B". I want another column of calculated data which is the differential between the number of "A"s and the number of "B"s up to that point, so just a countif()-countif() with the range increasing by one row. I can do this using =countif(A$2:A2, "A") - countif(A$2:A2, "B"), but it means I have to keep filling that equation down to cover any newly entered data, so I figured an array formula would be the best option to not have to do that. However when I try to use =arrayformula(countif(A$2:A, "A") - countif(A$2:A, "B")), it only populates a single cell with the difference counting the entire column. Is there a way to use an array formula so that it increases the range by one row for every row it populates?

Answer 1

=ARRAYFORMULA("A2:A"&ROW(A2:A))
This will give a dynamic string for the right range, which in theory, you should be able to wrap with INDIRECT, to plug into COUNTIF.
But COUNTIF only works in some circumstances with ARRAY FORMULA
Unfortunately, AFAIK, only if you use COUNTIF like this:
=ARRAYFORMULA(COUNTIF(A1:A100,A1:A100))
will it work as an array formula. Note how both the ranges in the arguments are the same.
MMULT
There may be a way along these lines with MMULT:
=ARRAYFORMULA(
MMULT(
(A2:A100 = TRANSPOSE(A2:A100)) * (ROW(A2:A100) >= TRANSPOSE(ROW(A2:A100))),
SIGN(ROW(A2:A100))
)
)
But I couldn't get that to work because I am not 100% sure on how to use MMULT in this way, but I have seen that type of solution elsewhere.
An Apps Script Workaround
As you have seen, what you want to achieve with sheet functions quickly gets very complicated. If you wanted to use more letters or different rules, it would get tough to maintain. Apps Script can make these things much simpler.
So here is a custom Apps Script function:
function myFunction() {
// Initializing
let file = SpreadsheetApp.getActive();
let sheet = file.getSheetByName("Sheet1");
var lastRow = sheet.getLastRow();
// This is the range of the As and Bs
let range = sheet.getRange(2,1, parseInt(lastRow) - 1,1)
let rows = range.getValues();
// Creating an object to keep track of the count
let tracker = {}
// This will be the output column
let newCol = []
rows.forEach(row => {
tracker[row[0]] += 1
// Adding a row to the output
newCol.push([tracker.A - tracker.B])
})
return newCol
}
Paste that into the script editor and you can use it like this:
Demo:
You can change the name of the function in the script editor according to what you need it for, just remember to call it with that name from the sheet.
References
Main Page
Sheets Guide
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Sheets Reference
INDIRECT
MMULT

Answer 2

try:
=ARRAYFORMULA(
COUNTIFS(A2:A, A2:A, A2:A, "A", ROW(A2:A), "<="&ROW(A2:A))-
COUNTIFS(A2:A, A2:A, A2:A, "B", ROW(A2:A), "<="&ROW(A2:A)))

Answer 3

Alternatively, you may this IF statement:
=ARRAYFORMULA(IF(K2:K<>"",K2:K*B294,""))
Results (Above formula is applied on L2 row onwards):
Source: https://blog.sheetgo.com/google-sheets-formulas/arrayformula-google-sheets/