Check the axis before subtracting matrix reference values

Define the task

When a worksheet contains sites in rows and instruments in columns, write out what each reference represents. A column-specific calibration offset must follow the instrument even if someone reorders the columns. Match identifiers and reject absent, duplicate or unmatched labels before converting a labeled table to a numeric matrix.

Carry out the check

Subtract the matching offset from every cell on its intended margin. In R a two-dimensional matrix uses margin 1 for rows and 2 for columns. Verify a cell from each axis by hand. Repeat with permuted column order. A square matrix is a particularly risky test case because a transposed offset can still have the expected length.

Worked hypothetical example

For a hypothetical first row of 12 and 30 units and instrument offsets of 2 and 5, the adjusted row is 10 and 25. Applying the first site's offset of 2 across that row instead yields 10 and 28. The first cell passes either implementation. Keep the second sentinel cell in the regression check.

Method checked 10 November 2026 against R documentation: Sweep out Array Summaries.