How to make plot legend have names instead of "y1, y2, ..., yn"

Much to my chagrin, after reading the Plots.jl Tutorial in its entirety I can’t get this to work:

histogram([[1,2,3,1],[1,2,2,2,2]],labels=["foo","bar"])

Gives (obviously I don’t want arrays for variable names):
hist1

Maybe I just need to name the input variables? Unfortunately the following doesn’t work either:

foo = [1,2,3,1]; bar = [1,2,2,2,2]
histogram([foo,bar])

Gives:
hist1

Make the vector of labels a row vector instead of a standard column vector.

Thanks @baggepinnen. That seems logical given the result of the first command, but the following commands give the same plot:

histogram([[1,2,3,1],[1,2,2,2,2]],labels=["foo";"bar"])
histogram([[1,2,3,1],[1,2,2,2,2]],labels=["foo","bar"])

None of those are row vectors, try space instead of comma or semicolon.

The semicolon still makes a vector, whereas you need a 1-row matrix:

julia> ["foo";"bar"] # vcat("foo", "bar"), which agrees with ["foo","bar"]
2-element Array{String,1}:
 "foo"
 "bar"

julia> ["foo" "bar"] # hcat("foo", "bar")
1×2 Array{String,2}:
 "foo"  "bar"

You could also write permutedims(["foo", "bar"]) if you already had the vector.

Note BTW that the reason this can’t work is that Julia doesn’t have non-standard evaluation. The function histogram has no way of seeing what variable names were used, all it gets (in this case) is a vector of vectors of numbers, after everything inside its () has been worked out.

perfect, thanks

Does anyone know why this design was chosen? It’s far more natural to write an array of labels with commas than to write a row matrix.

It seems to be consistent with line plots, where each column of a 2d array is a series. So it would make sense for each label to be a column. From the documentation:

x = 1:10; y = rand(10, 2) # 2 columns means two lines
plot(x, y, title = "Two Lines", label = ["Line 1" "Line 2"], lw = 3)

Histograms get converted into x-y data under the hood, making it non-obvious what the labels correspond to. But we can guess each resulting column is still a series, so the labels work in columns as well.