Plots.jl integration: grouping data leads to wrong errorbars

[lukas-weber]

(Originally I had opened JuliaPlots/Plots.jl#4917, but then I realized the recipe is actually in this repository.)

If you use the group keyword with Measurement data, the errorbars of different data points get silently mixed up:

using Measurements
using Plots

data = range(0, 1, 10) .± range(0, 1, 10)
ids = mod.(1:10, 2)

plot(
   plot(data, title="expected errorbars"),
   plot(data, group=ids, title="wrong errorbars")
)

[giordano]

I'm not really sure what's the expected result, I'm not familiar with the group option. Code of the plot recipe is at https://github.com/JuliaPhysics/Measurements.jl/blob/833064e4a4dca58be82ceaaa257d96a6b3708cfe/ext/MeasurementsRecipesBaseExt.jl, PR to fix the issue are welcome.