Allow values to get passed to hline/vline instead of vectors

[djsegal]

Right now you get an error:

scatter(rand(100))
hline!(0.5)

---

Cannot convert Float64 to series data for plotting

Stacktrace:
 [1] error(::String) at ./error.jl:33
 [2] prepareSeriesData(::Float64) at /Users/dan/.julia/packages/Plots/cc8wh/src/series.jl:14
 [3] convertToAnyVector(::Float64, ::Dict{Symbol,Any}) at /Users/dan/.julia/packages/Plots/cc8wh/src/series.jl:29
 [4] macro expansion at /Users/dan/.julia/packages/Plots/cc8wh/src/series.jl:129 [inlined]
 [5] apply_recipe(::Dict{Symbol,Any}, ::Type{Plots.SliceIt}, ::Nothing, ::Float64, ::Nothing) at /Users/dan/.julia/packages/RecipesBase/G4s6f/src/RecipesBase.jl:279

// this should just automatically cast the hline or vline like:

hline([0.5])

[BeastyBlacksmith]

If this is going to be done, we shouldn't specialize hline/vline, but generally allow things like scatter(0.2,0.3).

[mkborregaard]

Note that scatter(2) (using an Int rather than a float) does something different (opens an empty plot with 2 subplots).
I disagree with

this should just automatically cast the hline or vline

A distinction between vectors and scalars is exactly what makes julia nicer than R IMHO

[BeastyBlacksmith]

Note that scatter(2) (using an Int rather than a float) does something different (opens an empty plot with 2 subplots).

Which I do find surprising

[mkborregaard]

Maybe? At least it's the current behaviour and some users depend on it (useful for live updating plots where you gradually push to the series)

[daschw]

plt = plot(2) creates a plot with 2 empty series (in one subplot). Then you can push a point to the ith series with push!(plt, i, (x, y)).

[mkborregaard]

haha thanks @daschw I must have misremembered or used it with layout = 2

[BeastyBlacksmith]

duplicate of #2129

[Gyoshi]

I would find it much more intuitive if the methods were at least called hlines and vlines to indicate that they take an array of values.

Well, maybe that is not the ideal solution, but when so many things "just work", it is honestly flabbergasting not to have something as straightforward as hline!(3.1) work.

[juliohm]

Should this be closed as a duplicate?