Function regular_axis_through 

pub fn regular_axis_through(
    coords: &[f64],
    f: impl Fn(f64) -> f64,
    through: &str,
    cell: CellConvention,
    tolerance: Tolerance,
) -> (Option<Positions>, Report)

Test whether a 1D coordinate vector is evenly spaced after applying f to every value (for example latitude to Mercator y). through names the frame f maps into. On success the returned positions are in that frame.