Cannot mix DateTime and NaNs to get unconnected line segments

[cstjean]

As shown in the docs, it's possible to draw unconnected segments in a single call by adding NaNs for segment breaks. Unfortunately, this fails with DateTime axes.

function rectangle_from_coords(xb,yb,xt,yt)
    Any[
        xb yb
        xt yb
        xt yt
        xb yt
        xb yb
        NaN NaN
    ]
end

d(day) = DateTime(2017, 1, day)
some_rects=[
    rectangle_from_coords(d(1) ,d(1) ,d(5) ,d(5) )
    rectangle_from_coords(d(10),d(10),d(15),d(15))
    ]
plot(some_rects[:,1], some_rects[:,2],label="some group")

gives

MethodError: no method matching value(::Float64)
Closest candidates are:
  value(::Base.Dates.Time) at dates/accessors.jl:46
  value(::Base.Dates.Period) at dates/periods.jl:4
  value(::Base.Dates.TimeType) at dates/accessors.jl:45

Stacktrace:
 [1] collect_to!(::Array{Int64,1}, ::Base.Generator{Array{Any,1},Plots.##294#295}, ::Int64, ::Int64) at ./array.jl:508
 [2] _collect(::Array{Any,1}, ::Base.Generator{Array{Any,1},Plots.##294#295}, ::Base.EltypeUnknown, ::Base.HasShape) at ./array.jl:489
 [3] map(::Function, ::Array{Any,1}) at ./abstractarray.jl:1868
 [4] _apply_type_recipe(::Dict{Symbol,Any}, ::Array{Any,1}) at /home/cedric/.julia/v0.6/Plots/src/series.jl:193
 [5] macro expansion at /home/cedric/.julia/v0.6/Plots/src/series.jl:235 [inlined]
 [6] apply_recipe(::Dict{Symbol,Any}, ::Array{Any,1}, ::Array{Any,1}) at /home/cedric/.julia/v0.6/RecipesBase/src/RecipesBase.jl:287
 [7] _process_userrecipes(::Plots.Plot{Plots.GRBackend}, ::Dict{Symbol,Any}, ::Tuple{Array{Any,1},Array{Any,1}}) at /home/cedric/.julia/v0.6/Plots/src/pipeline.jl:81
 [8] _plot!(::Plots.Plot{Plots.GRBackend}, ::Dict{Symbol,Any}, ::Tuple{Array{Any,1},Array{Any,1}}) at /home/cedric/.julia/v0.6/Plots/src/plot.jl:179
 [9] #plot#192(::Array{Any,1}, ::Function, ::Array{Any,1}, ::Vararg{Array{Any,1},N} where N) at /home/cedric/.julia/v0.6/Plots/src/plot.jl:58
 [10] (::RecipesBase.#kw##plot)(::Array{Any,1}, ::RecipesBase.#plot, ::Array{Any,1}, ::Array{Any,1}, ::Vararg{Array{Any,1},N} where N) at ./<missing>:0
 [11] include_string(::String, ::String) at ./loading.jl:522

Similary for strings:

> plot([1,2,3, 3], ["A", "A", "B", NaN])
No user recipe defined for String

Stacktrace:
 [1] convertToAnyVector(::String, ::Dict{Symbol,Any}) at /home/cedric/.julia/v0.6/Plots/src/series.jl:14
 [2] copy!(::Array{Any,1}, ::Base.Generator{Array{Any,1},Plots.##203#205{Dict{Symbol,Any}}}) at ./abstractarray.jl:573
 [3] convertToAnyVector(::Array{Any,1}, ::Dict{Symbol,Any}) at /home/cedric/.julia/v0.6/Plots/src/series.jl:58
 [4] macro expansion at /home/cedric/.julia/v0.6/Plots/src/series.jl:132 [inlined]
 [5] apply_recipe(::Dict{Symbol,Any}, ::Type{Plots.SliceIt}, ::Array{Int64,1}, ::Array{Any,1}, ::Void) at /home/cedric/.julia/v0.6/RecipesBase/src/RecipesBase.jl:287
 [6] _process_userrecipes(::Plots.Plot{Plots.GRBackend}, ::Dict{Symbol,Any}, ::Tuple{Array{Int64,1},Array{Any,1}}) at /home/cedric/.julia/v0.6/Plots/src/pipeline.jl:81
 [7] _plot!(::Plots.Plot{Plots.GRBackend}, ::Dict{Symbol,Any}, ::Tuple{Array{Int64,1},Array{Any,1}}) at /home/cedric/.julia/v0.6/Plots/src/plot.jl:179

[cstjean]

Work-around by passing a vector of alpha values: plot([1,2,3,4], ["A", "A", "B", "B"], alpha=[1.0, 1, 0, 0])

[mkborregaard]

Maybe a longer term approach could be to allow passing Missing that would then be reinterpreted as NaN when the Dates are converted to Floats by the DateFormatter?