Wrong units

[jariji]

  [13f3f980] CairoMakie v0.12.5
  [1986cc42] Unitful v1.21.0


julia> scatter(rand(5)u"m/s", rand(5)u"m/s")

The units are wrong.

[SimonDanisch]

Why it switches to decimeter is because the default is to automatically switch to the best unit to represent the number range.
Why it drops the second is not really clear to me...
You could have a look at: https://github.com/MakieOrg/Makie.jl/blob/master/src/dim-converts/unitful-integration.jl
And see where it goes wrong!

[ffreyer]

It's one of the base_unit() calls.

Makie.jl/src/dim-converts/unitful-integration.jl

Lines 14 to 16 in 4c4eaa1

	base_unit(q::Quantity) = base_unit(typeof(q))
	base_unit(::Type{Quantity{NumT, DimT, U}}) where {NumT, DimT, U} = base_unit(U)
	base_unit(::Type{Unitful.FreeUnits{U, DimT, nothing}}) where {DimT, U} = U[1]

It goes through these 3 in order where in the last one U = (m, s^-1), so that indexing just grabs m

[ffreyer]

It looks like most of this is for adjusting unit prefixes to the range of numbers given. E.g. changing 10000m .. 54000m to 10km .. 54km. I wonder if we should just drop those conversions.
It seems difficult to apply them to compound units - e.g. if you have "A * B / C", should A, B or C get a prefix? Some people may also supply specific prefixes on purpose because they are commonly used (e.g. g/cm^3). It also looks like this is not generic atm, i.e. we'd have to define valid prefixes for every unit and add special cases to avoid things like dft (deci-feet).

[jariji]

Yeah keeping the user's units seems good.

[abhro]

Is there an option to do it at the top (or right) of the axes? I mean in the style that MATLAB does power of 10 representations (linear plot, scaled), then putting the units on top of the axis might help (see first image of https://tutorial45.com/matlab-plot-colors-and-styles/)

[aplavin]

Agree, it would be both more familiar to many readers and less cluttered to show units once per axes – #3890.

[nathanrboyer]

There are no circumstances under which I want to plot deka-feet. 😑
Is there a quick switch to get ft back, and can d, c, da, and h be excluded from the automatic conversions?

[ffreyer]

You can turn off automatic conversions if you create the conversion manually. It's explained in ?Makie.UnitfulConversion

[nathanrboyer]

Okay, thanks. I got that working. I still think conversions from 10^-2 through 10^2 should be automatically avoided though.