Use xunit, yunit kwargs better; make guide=nothing produce no label at all

Author: Ickaser

ext/UnitfulExt.jl

@@ -29,21 +29,20 @@ end
 
 function fixaxis!(attr, x, axisletter)
     # Attribute keys
-    axislabel = Symbol(axisletter, :guide) # xguide, yguide, zguide
-    axislims = Symbol(axisletter, :lims)   # xlims, ylims, zlims
-    axisticks = Symbol(axisletter, :ticks) # xticks, yticks, zticks
     err = Symbol(axisletter, :error)       # xerror, yerror, zerror
     axisunit = Symbol(axisletter, :unit)   # xunit, yunit, zunit
     axis = Symbol(axisletter, :axis)       # xaxis, yaxis, zaxis
-    u = get!(attr, axisunit, _unit(eltype(x)))  # get the unit
-    # if the subplot already exists with data, use that unit instead
+    # if the subplot already exists with data, use that unit
     sp = get(attr, :subplot, 1)
-    if sp ≤ length(attr[:plot_object]) && attr[:plot_object].n > 0
+    if sp ≤ length(attr[:plot_object])
         spu = getaxisunit(attr[:plot_object][sp][axis])
         if !isnothing(spu)
             u = spu
+        else # Subplot exists but doesn't have a unit yet
+            u = get!(attr, axisunit, _unit(eltype(x)))  # get the unit
         end
-        attr[axisunit] = u  # update the unit in the attributes
+    else # Subplot doesn't exist yet, so create it with given unit
+        u = get!(attr, axisunit, _unit(eltype(x)))  # get the unit
     end
     # fix the attributes: labels, lims, ticks, marker/line stuff, etc.
     ustripattribute!(attr, err, u)

src/axes.jl

@@ -95,6 +95,11 @@ function attr!(axis::Axis, args...; kw...)
             plotattributes[k] = (Dates.value(v[1]), Dates.value(v[2]))
         elseif k === :guide && v isa AbstractString && isempty(v)
             plotattributes[k] = protectedstring(v)
+        elseif k === :unit 
+            if !isnothing(plotattributes[k]) && plotattributes[k] != v
+                @warn "Overriding unit for $(axis[:letter]) axis: $(plotattributes[k]) -> $v.  This will produce a plot, but series plotted before the override cannot update and will therefore be incorrectly treated as if they had the new units."
+            end
+            plotattributes[k] = v
         else
             plotattributes[k] = v
         end
@@ -114,7 +119,9 @@ Base.show(io::IO, axis::Axis) = dumpdict(io, axis.plotattributes, "Axis")
 ignorenan_extrema(axis::Axis) = (ex = axis[:extrema]; (ex.emin, ex.emax))
 
 function get_guide(axis::Axis)
-    if isnothing(axis[:unit]) || axis[:guide] isa ProtectedString ||
+    if isnothing(axis[:guide])
+        return ""
+    elseif isnothing(axis[:unit]) || axis[:guide] isa ProtectedString ||
         axis[:unitformat] == :none 
         return axis[:guide]
     else

src/layouts.jl

@@ -664,8 +664,8 @@ function twin(sp, letter)
     tax[:grid] = false
     tax[:showaxis] = false
     tax[:ticks] = :none
-    tax[:unitformat] = :none
     tax[:unit] = orig_sp[get_attr_symbol(letter, :axis)][:unit]
+    tax[:guide] = nothing
     oax[:grid] = false
     oax[:mirror] = true
     twin_sp[:background_color_inside] = RGBA{Float64}(0, 0, 0, 0)