> Why won't you just take cases[i - 1] here?

Example:
- values (5): 1.0, 2.0, -, 1.0, 1,0
- expected x-scale (4): 0.5, -, 2.0, 1.0
- bad x-scale result: 0.5, -, -, 1.0

Without missed results, `cases[i - 1]` is OK.

> First, this contradicts the column header.

OK, I will change column header to "... vs previous (...)" in progress mode.

> Second, it means that different values in the same column are comparing different test runs, which is bound to lead to confusion.

See the example above. I want to track progress. This "hint" is only for missed/failed results.