[BUG] Specifying 'errorbar' with asymmetric error bar data with 'Unitful' values returns DimensionError

[jmtlawrie]

Details

Hello!

Plotting data with Unitful.jl units and specifiying to plot asymmetrical error bars for these data, giving the errorbar data also as data with Unitful.jl units results in a DimensionError due to attempting to subtract incompatible Unitful.Quantity from each other.

My best guess (so far) is that something occurs (or doesn't occur, but it should) within UnitfulExt.jl. I looked specifically at when the attributes are fixed by the function fixaxis!, but unfortunately I couldn't quite understand why it is only asymmetrical error bar data which seem to cause an issue.

A workaround is to pre-process the error data to ensure that the data are converted to the same unit as the axis, and that the Unitful.jl units are removed before plot() is called.

Thanks!

J

Minimum working example

using Plots
using Unitful

x = [1.0, 2.0]
y = x .* u"m"
ϵₛ = y         # Symmetric error bar data
ϵₗ = y          # Lower error bound data
ϵₕ = ϵₗ ./ 2     # Upper error bound data

# Symmetric error bar data with Unitful units -> no problem
plot(x, y; yerror = ϵₛ)

# Asymmetric error bar data with Unitful units -> returns 'DimensionError' attempting to subtract unitless value from value with units
plot(x, y; yerror = (ϵₗ, ϵₕ)) 

# Asymmetric error bar data without Unitful units -> plots successfully, but user must ensure the error bar values match the axis units 
plot(x, y; yerror = map(t -> ustrip.(t), (ϵₗ, ϵₕ)))

Full error message:

ERROR: DimensionError: 1.0 and 1.0 m are not dimensionally compatible.
Stacktrace:
  [1] -(x::Quantity{Float64, NoDims, Unitful.FreeUnits{…}}, y::Quantity{Float64, 𝐋, Unitful.FreeUnits{…}})
    @ Unitful ~/.julia/packages/Unitful/6r8Hq/src/quantities.jl:137
  [2] -(x::Float64, y::Quantity{Float64, 𝐋, Unitful.FreeUnits{(m,), 𝐋, nothing}})
    @ Base ./promotion.jl:424
  [3] error_coords(errorbar::Vector{Tuple{Quantity{…}, Quantity{…}}}, errordata::Vector{Float64}, otherdata::Vector{Float64})
    @ Plots ~/.julia/packages/Plots/du2dt/src/recipes.jl:1132
  [4] macro expansion
    @ ~/.julia/packages/Plots/du2dt/src/recipes.jl:1167 [inlined]
  [5] apply_recipe(plotattributes::AbstractDict{Symbol, Any}, ::Type{Val{:yerror}}, x::Any, y::Any, z::Any)
    @ Plots ~/.julia/packages/RecipesBase/BRe07/src/RecipesBase.jl:300
  [6] _process_seriesrecipe(plt::Any, plotattributes::Any)
    @ RecipesPipeline ~/.julia/packages/RecipesPipeline/BGM3l/src/series_recipe.jl:50
  [7] _process_seriesrecipes!(plt::Any, kw_list::Any)
    @ RecipesPipeline ~/.julia/packages/RecipesPipeline/BGM3l/src/series_recipe.jl:27
  [8] recipe_pipeline!(plt::Any, plotattributes::Any, args::Any)
    @ RecipesPipeline ~/.julia/packages/RecipesPipeline/BGM3l/src/RecipesPipeline.jl:99
  [9] _plot!(plt::Plots.Plot, plotattributes::Any, args::Any)
    @ Plots ~/.julia/packages/Plots/du2dt/src/plot.jl:223
 [10] plot(::Any, ::Vararg{Any}; kw...)
    @ Plots ~/.julia/packages/Plots/du2dt/src/plot.jl:102
 [11] top-level scope
    @ ~/Desktop/Projects/cuddly-journey/UnitfulPlots_test.jl:12
Some type information was truncated. Use `show(err)` to see complete types.

Backends

This bug occurs on ( insert x below )

Backend	yes	no	untested
gr (default)	x
pythonplot			x
plotlyjs			x
pgfplotsx			x
unicodeplots			x
inspectdr			x
gaston			x

Versions

Plots.jl version:

[91a5bcdd] Plots v1.40.5

Backend version (]st -m <backend(s)>):

[28b8d3ca] GR v0.73.6

Output of versioninfo():

julia> versioninfo()
Julia Version 1.10.3
Commit 0b4590a5507 (2024-04-30 10:59 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (x86_64-apple-darwin22.4.0)
  CPU: 4 × Intel(R) Core(TM) i5-5250U CPU @ 1.60GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, broadwell)
Threads: 1 default, 0 interactive, 1 GC (on 4 virtual cores)
Environment:
  JULIA_EDITOR = code
  JULIA_NUM_THREADS =