LET / LAMBDA / SEQUENCE — Excel guide
The programmable layer (365): name intermediate steps, define your own functions, and generate arrays from thin air. Where Excel formulas turn into a real language.
LET
Name values inside a formula — compute once, reuse, read clearly.
- The FINAL argument is the result; everything before it is definitions.
- Later names can use earlier ones — a pipeline of steps.
- Names can't look like cell references (A1 is taken).
LAMBDA
Define a reusable custom function — no VBA.
- Save one under a name in Name Manager and =KILOS_TO_LBS(A2) works sheet-wide.
- Named LAMBDAs can call themselves — recursion, the 'repeat until done' Excel never had.
- The helper family: MAP (transform each), BYROW/BYCOL (aggregate each), SCAN (running values), REDUCE (final value).
SEQUENCE
Generate number series of any shape.
- SEQUENCE(4, 1, 0, 25) → 0, 25, 50, 75. Negative steps count down.
- A column SEQUENCE times a row SEQUENCE broadcasts a whole grid — instant times tables.
- Feed it to INDEX for every-Nth sampling: INDEX(col, SEQUENCE(33, 1, 1, 3)).