BYROW

What it does

BYROW(array, lambda)

BYROW(array, lambda) applies a one-parameter lambda to each entire row and returns one result per row in a single column. For r input rows and c input columns, a scalar result from each invocation produces an r-by-one output.

=BYROW({1,2;3,4},LAMBDA(row,SUM(row))) returns the column {3;7}. The lambda receives a row array, not one cell at a time.

Try it

Change the sum to MAX(row) or AVERAGE(row). Compare the output shape with BYCOL, which passes columns instead and returns a row.

Quirks

Microsoft documents incorrect lambda parameters as #VALUE! and a result that is not a single value as #CALC!. A row-shaped input to the lambda does not mean that the lambda may return an arbitrarily shaped array.

Direct error arguments are checked before ordinary array elements. The recorded BYROW(#N/A,#VALUE!) returns #N/A, while BYROW({#N/A},2) returns #VALUE! for the invalid lambda. Keep those cases distinct when validating a helper call.

How to implement

Expose one row-shaped view of the input at a time, invoke the one-parameter callable, and store its scalar answer in the corresponding position of a one-column result. Preserve the callable and any references the operation requires instead of reconstructing them from cell display.

Validate result shape per invocation. Do not flatten a nested result silently or reduce a returned error into a logical. Keep direct argument error handling separate from errors found inside a row. Share this machinery with BYCOL by changing which dimension is exposed and which output dimension is retained.

Rust code

4 byrow_fn "BYROW" (2, 2) [R "array", R "lambda"] resume byrow_resume => byrow_start; |s, a, sv| { run(s, byrow_start(s, a, sv), sv) }

fn byrow_start(
    site: &Site<'_>,
    a: &[CalcValue],
    sv: &mut EvalServices<'_>,
) -> Step<Box<dyn KernelTask>> {
    by_task(site, a, sv, false)
}

No implementation has been published with a Handbook test suite for this function.

Version differences

Microsoft lists BYROW for Microsoft 365 and Excel 2024 on Windows and Mac. The error examples below are observations on their named build, not a cross-version comparison.

Alternatives

BYCOL passes whole columns. MAP passes individual positions and preserves shape. REDUCE accumulates over the array rather than producing one answer per row.

Named variants

No named variants are recorded yet.