Posts about Iterator Functions.
REDUCE is the most powerful of the functional array functions and the most overlooked. The lambda which means you can accumulate strings, and replace calculations that used to need VBA.
MAP takes your LAMBDA and runs it on every element in an array. No helper columns, no dragging formulas, no VBA loops. It's the Excel equivalent of a functional programming pattern, and once you've used it, going back to column-by-column formulas feels like a step backwards.
BYROW hands your function an entire row at a time. BYCOL does the same by column. Together they replace an entire category of 'drag this formula down and keep it updated' work — and when you combin…
BYROW hands your function an entire row at a time — which means 'apply this logic to every row in this range' is one formula in one cell. No dragging, no CTRL+SHIFT+ENTER, no missing the last row w…
SCAN hands you every intermediate result as it accumulates — which means a running total is one formula that spills down the column. No helper rows, no dragging, no breaking when someone inserts a …
SUMX, AVERAGEX, MAXX — these functions bring row context back into a measure, which sounds helpful until they don't behave the way you expect inside a CALCULATE. Part 4 closes the series with the p…