Sequence number for each different value in a colum - google-sheets

Question

I have an Input column with a sequence of two different letters. As result I want to get something like on the picture. This formulas I will use with ARRAYFORMULA to get unlimited count of rows. To get BLOCK № I was trying to use =COUNTIFS($B$2:B2,"N") but it works only if I copy the formula manually down the column, but if I do:
=ARRAYFORMULA(COUNTIFS(($B$2):(B2:B),"N"))
It doesn't work.
How can I replicate the behavior of this function without needed to manually copy it?

Answer 1

I'd recommend writing a script to fill the Block Nos.
I'll assume the topmost letter begins at cell input!A4 and you want the Block Nos from cell input!C5 and below. Go to the menu bar of the spreadsheet and select Script Editor. Then write the following scripts:
//the main function
function writeBlocks() {
var sheet = SpreadsheetApp.getActiveSpreadsheet()
.getSheetByName('input');
var numRows = sheet.getLastRow();
var startRow = 4;
var inputCol = 1;
var outputCol = 3;
var block = 0;
//clear old Block Nos
sheet.getRange(startRow, outputCol, numRows - 3, 1)
.clearContent();
//recalculate LastRow in case there are fewer new inputs than old outputs
numRows = sheet.getLastRow();
//get input data
var input = sheet.getRange(startRow, inputCol, numRows - 3, 1)
.getValues;
//write output data
for (var i = 0; i < input.length; i++) {
block += input[i] == "N" ? 1 : 0;
sheet.getRange(startRow + i, outputCol)
.setValue(block);
}
}
//create new menu
function onOpen() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var menuEntries = [];
menuEntries.push({name: "Calculate blocks", functionName: "writeBlocks"});
ss.addMenu("Custom functions", menuEntries);
}
Save it all, refresh the spreadsheet, and there should be a new option on the menu bar. When you select that option, it will clear the old Block Nos and generate new ones based on the current inputs. Hope this helps.