Named functions: your team's own formulas

Once a LAMBDA works, you can give it a name and use it like a built-in function. This is how a team writes down its rules once: what counts as a qualified lead, how ROAS handles zero spend, which fiscal quarter a date falls in.

1. Open Data › Named functions and click Add new function.
2. Name it in capitals, like ROAS.
3. Add argument placeholders: spend, revenue.
4. Write the formula definition using the placeholders: =IF(spend=0, 0, revenue/spend)
5. Add a description and an example, then save.

Now anyone in the file can type =ROAS(B2, C2), and it shows up in autocomplete with your description. It works inside other formulas too: =MAP(B2:B50, C2:C50, LAMBDA(s, r, ROAS(s, r))).

Why it matters:

• One definition. Change the rule in Named functions and every cell that uses it updates. No find-and-replace across tabs.
• Readable sheets. =FISCAL_QUARTER(A2) explains itself. The nested IF it replaces doesn't.
• Portable. Data › Named functions › Import function copies them from another file, so a team can keep a library sheet of house functions.

A named function can call other named functions, and its definition can use LET to stay readable. If the logic needs a loop, an outside service or more than a formula can express, that's when you reach for an Apps Script custom function, covered at the end of this level.

Named functions live in the file, so this practice grid can't save one. Try it in your own sheet: build ROAS, then use it in a MAP.