Wide Format

Wide format spreads data across many columns: typically one row per entity, with each measurement in its own column. A student's three test scores become one row with three columns (test1, test2, test3).

Wide is easy for people to read and good for side-by-side comparison, which is why spreadsheets default to it. But it gets awkward for analysis — adding a fourth test means a new column and rewritten code. Real work constantly converts between wide and long with reshape operations, picking whichever shape the next step needs.