Data for Aug 1  Data for Aug 2  Data for Aug 3  Desired Output
1               5               8               14
2               4               9               15
3               3               10              16
4               2               11              17
5               1               12              18

Let’s say the values starts at Row 2 Column A in a sheet called Sheet1.

let ss = SpreadsheetApp.getActiveSpreadsheet();
let sheet1 = ss.getSheetByName('Sheet1');
let values = sheet1.getRange(2,1,sheet1.getMaxRows()-1,3).getValues();

How do I get the desired output above? The column numbers and column counts are not fixed and may change according to a date range selection. For example, a user may choose to find only the sum from Aug 2 to Aug 3, or from Aug 1 to 3.

I have seen posts about getting the sum of all rows in a column using for loop or reduce. But haven’t seen a post about cumulative sum per row across a group columns.