Cannot convert Float64 to series data for plotting in 0.27.0

[homocomputeris]

using Plots
ints = collect(1:3)
floats = float(ints)
plot(ints...)
plot(floats...)

gives

Cannot convert Float64 to series data for plotting
Stacktrace:
 [1] prepareSeriesData(::Float64) at /home/user/.julia/packages/Plots/Iuc9S/src/series.jl:15
 [2] convertToAnyVector(::Float64, ::Dict{Symbol,Any}) at /home/user/.julia/packages/Plots/Iuc9S/src/series.jl:26
 [3] macro expansion at /home/user/.julia/packages/Plots/Iuc9S/src/series.jl:129 [inlined]
 [4] apply_recipe(::Dict{Symbol,Any}, ::Type{Plots.SliceIt}, ::Float64, ::Float64, ::Float64) at /home/user/.julia/packages/RecipesBase/zBoFG/src/RecipesBase.jl:275
 [5] _process_userrecipes(::Plots.Plot{Plots.GRBackend}, ::Dict{Symbol,Any}, ::Tuple{Float64,Float64,Float64}) at /home/user/.julia/packages/Plots/Iuc9S/src/pipeline.jl:83
 [6] _plot!(::Plots.Plot{Plots.GRBackend}, ::Dict{Symbol,Any}, ::Tuple{Float64,Float64,Float64}) at /home/user/.julia/packages/Plots/Iuc9S/src/plot.jl:178
 [7] #plot#137(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(plot), ::Float64, ::Vararg{Float64,N} where N) at /home/user/.julia/packages/Plots/Iuc9S/src/plot.jl:57
 [8] plot(::Float64, ::Float64, ::Vararg{Float64,N} where N) at /home/user/.julia/packages/Plots/Iuc9S/src/plot.jl:51
 [9] top-level scope at In[56]:5

  Status `~/.julia/environments/v1.2/Project.toml`
  [682c06a0] JSON v0.21.0
  [91a5bcdd] Plots v0.27.0

[yha]

What is the expected behavior? Perhaps you mean plot(floats), without the ellipsis?
I'm surprised plot(ints...) doesn't error, but I think its behavior is also a bit surprising.

[homocomputeris]

If I want to plot a point in 3D space, what command am I supposed to use? plot(ints...) does what I want.
Where are the docs for plot? ?plot is useless.

julia
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.2.0 (2019-08-20)
 _/ |\__'_|_|_|\__'_|  |  
|__/                   |

julia> using Plots

julia> x = float(collect(1:3))
3-element Array{Float64,1}:
 1.0
 2.0
 3.0

julia> plot(x)
# plot of a line in 2D appears

julia> plot(x...)
ERROR: Cannot convert Float64 to series data for plotting
Stacktrace:
 [1] prepareSeriesData(::Float64) at /home/nik/.julia/packages/Plots/Iuc9S/src/series.jl:15
 [2] convertToAnyVector(::Float64, ::Dict{Symbol,Any}) at /home/nik/.julia/packages/Plots/Iuc9S/src/series.jl:26
 [3] macro expansion at /home/nik/.julia/packages/Plots/Iuc9S/src/series.jl:129 [inlined]
 [4] apply_recipe(::Dict{Symbol,Any}, ::Type{Plots.SliceIt}, ::Float64, ::Float64, ::Float64) at /home/nik/.julia/packages/RecipesBase/zBoFG/src/RecipesBase.jl:275
 [5] _process_userrecipes(::Plots.Plot{Plots.GRBackend}, ::Dict{Symbol,Any}, ::Tuple{Float64,Float64,Float64}) at /home/nik/.julia/packages/Plots/Iuc9S/src/pipeline.jl:83
 [6] _plot!(::Plots.Plot{Plots.GRBackend}, ::Dict{Symbol,Any}, ::Tuple{Float64,Float64,Float64}) at /home/nik/.julia/packages/Plots/Iuc9S/src/plot.jl:178
 [7] #plot#137(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(plot), ::Float64, ::Vararg{Float64,N} where N) at /home/nik/.julia/packages/Plots/Iuc9S/src/plot.jl:57
 [8] plot(::Float64, ::Float64, ::Vararg{Float64,N} where N) at /home/nik/.julia/packages/Plots/Iuc9S/src/plot.jl:51
 [9] top-level scope at REPL[4]:1

julia> plot3d(x)
Error showing value of type Plots.Plot{Plots.GRBackend}:
ERROR: MethodError: no method matching length(::Nothing)
Closest candidates are:
  length(::Core.SimpleVector) at essentials.jl:597
  length(::Base.MethodList) at reflection.jl:819
  length(::Core.MethodTable) at reflection.jl:893
  ...
Stacktrace:
 [1] map(::typeof(length), ::Tuple{UnitRange{Int64},Array{Float64,1},Nothing}) at ./tuple.jl:141
 [2] iter_segments(::UnitRange{Int64}, ::Array{Float64,1}, ::Vararg{Any,N} where N) at /home/nik/.julia/packages/Plots/Iuc9S/src/utils.jl:190
 [3] iter_segments(::Plots.Series) at /home/nik/.julia/packages/Plots/Iuc9S/src/utils.jl:207
 [4] gr_display(::Plots.Subplot{Plots.GRBackend}, ::Measures.Length{:mm,Float64}, ::Measures.Length{:mm,Float64}, ::Array{Float64,1}) at /home/nik/.julia/packages/Plots/Iuc9S/src/backends/gr.jl:1363
 [5] gr_display(::Plots.Plot{Plots.GRBackend}, ::String) at /home/nik/.julia/packages/Plots/Iuc9S/src/backends/gr.jl:685
 [6] gr_display at /home/nik/.julia/packages/Plots/Iuc9S/src/backends/gr.jl:643 [inlined]
 [7] _display(::Plots.Plot{Plots.GRBackend}) at /home/nik/.julia/packages/Plots/Iuc9S/src/backends/gr.jl:1629
 [8] display(::Plots.PlotsDisplay, ::Plots.Plot{Plots.GRBackend}) at /home/nik/.julia/packages/Plots/Iuc9S/src/output.jl:144
 [9] #invokelatest#1 at ./essentials.jl:790 [inlined]
 [10] invokelatest at ./essentials.jl:789 [inlined]
 [11] print_response(::IO, ::Any, ::Bool, ::Bool, ::Any) at /build/julia/src/julia-1.2.0/usr/share/julia/stdlib/v1.2/REPL/src/REPL.jl:156
 [12] (::getfield(REPL, Symbol("#do_respond#38")){Bool,getfield(REPL, Symbol("##48#57")){REPL.LineEditREPL,REPL.REPLHistoryProvider},REPL.LineEditREPL,REPL.LineEdit.Prompt})(::Any, ::Any, ::Any) at /build/julia/src/julia-1.2.0/usr/share/julia/stdlib/v1.2/REPL/src/REPL.jl:718

julia> plot3d(x...)
ERROR: Cannot convert Float64 to series data for plotting
Stacktrace:
 [1] prepareSeriesData(::Float64) at /home/nik/.julia/packages/Plots/Iuc9S/src/series.jl:15
 [2] convertToAnyVector(::Float64, ::Dict{Symbol,Any}) at /home/nik/.julia/packages/Plots/Iuc9S/src/series.jl:26
 [3] macro expansion at /home/nik/.julia/packages/Plots/Iuc9S/src/series.jl:129 [inlined]
 [4] apply_recipe(::Dict{Symbol,Any}, ::Type{Plots.SliceIt}, ::Float64, ::Float64, ::Float64) at /home/nik/.julia/packages/RecipesBase/zBoFG/src/RecipesBase.jl:275
 [5] _process_userrecipes(::Plots.Plot{Plots.GRBackend}, ::Dict{Symbol,Any}, ::Tuple{Float64,Float64,Float64}) at /home/nik/.julia/packages/Plots/Iuc9S/src/pipeline.jl:83
 [6] _plot!(::Plots.Plot{Plots.GRBackend}, ::Dict{Symbol,Any}, ::Tuple{Float64,Float64,Float64}) at /home/nik/.julia/packages/Plots/Iuc9S/src/plot.jl:178
 [7] #plot#137(::Base.Iterators.Pairs{Symbol,Symbol,Tuple{Symbol},NamedTuple{(:seriestype,),Tuple{Symbol}}}, ::typeof(plot), ::Float64, ::Vararg{Float64,N} where N) at /home/nik/.julia/packages/Plots/Iuc9S/src/plot.jl:57
 [8] (::getfield(RecipesBase, Symbol("#kw##plot")))(::NamedTuple{(:seriestype,),Tuple{Symbol}}, ::typeof(plot), ::Float64, ::Float64, ::Vararg{Float64,N} where N) at ./none:0
 [9] #plot3d#442(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(plot3d), ::Float64, ::Vararg{Float64,N} where N) at /home/nik/.julia/packages/Plots/Iuc9S/src/shorthands.jl:387
 [10] plot3d(::Float64, ::Vararg{Float64,N} where N) at /home/nik/.julia/packages/Plots/Iuc9S/src/shorthands.jl:387
 [11] top-level scope at REPL[6]:1

[yha]

To plot a single point, you still need to pass a vector for each of x,y,z.
You should also use scatter, or specify markers, since by default plot only plots lines between points and won't show anything for a single point. So either of the following:

scatter([1],[2],[3])
plot([1],[2],[3], marker=:circle)

You can also pass points as tuple of coordinates, like plot([(1,2,3)]). So if you already have the coordinates in a vector as in your example,

x = [1,2,3]
scatter([tuple(x...)])

[homocomputeris]

In the end, should

plot(ints...)
plot(floats...)

have the same of different behavior or not? Should both raise an error?

[yha]

plot(n), with a single integer n, creates n empty series. This behavior is deliberate and documented.
plot(ints...) apparently does the same thing as plot(maximum(ints)), which is probably a bug.
plot(floats...) should and does error. Maybe it can be changed to mean plotting a single point, but this conflicts with the current meaning of plot(n) (see the discussion in #2129).

[homocomputeris]

Thanks for the explanation.

plot(n), with a single integer n, creates n empty series. This behavior is deliberate and documented.

I'd say this semantics is rather counterintuitive. If plot(series1, series2) is a valid plot, I'd expect that plot(int) is a plot of a point versus an axis or nothing at all, but not an plot with n empty series.