Add stephist with related Stairs plot type, and Volume plot type

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Added `Volume`, `Stairs` aesthetic mapping and `stephistogram` analysis [#572](https://github.com/MakieOrg/AlgebraOfGraphics.jl/pull/572).
+
 ## v0.8.12 - 2024-10-07
 
 - Added `legend` keyword in `visual` to allow overriding legend element attributes [#570](https://github.com/MakieOrg/AlgebraOfGraphics.jl/pull/570).

src/AlgebraOfGraphics.jl

@@ -34,7 +34,7 @@ export hideinnerdecorations!, deleteemptyaxes!
 export Layer, Layers, ProcessedLayer, ProcessedLayers
 export Entry, AxisEntries
 export renamer, sorter, nonnumeric, verbatim, presorted
-export density, histogram, linear, smooth, expectation, frequency, contours, filled_contours
+export density, histogram, stephistogram, linear, smooth, expectation, frequency, contours, filled_contours
 export visual, data, geodata, dims, mapping
 export datetimeticks
 export draw, draw!
@@ -70,6 +70,7 @@ include("transformations/frequency.jl")
 include("transformations/expectation.jl")
 include("transformations/contours.jl")
 include("transformations/filled_contours.jl")
+include("transformations/stephistogram.jl")
 include("guides/guides.jl")
 include("guides/legend.jl")
 include("guides/colorbar.jl")

src/aesthetics.jl

@@ -166,6 +166,14 @@
     ])
 end
 
+function aesthetic_mapping(::Type{Stairs}, ::Normal, ::Normal)
+    dictionary([
+        pointlike_positionals(2)...,
+        :color => AesColor,
+        :linestyle => AesLineStyle,
+    ])
+end
+
 function aesthetic_mapping(::Type{HLines}, ::Normal)
     dictionary([
         1 => AesY,
@@ -218,6 +226,15 @@
     ])
 end
 
+function aesthetic_mapping(::Type{Volume}, ::Normal, ::Normal, ::Normal, ::Normal)
+    dictionary([
+        1 => AesX,
+        2 => AesY,
+        3 => AesZ,
+        4 => AesVolumeColor, # set to AesColor would not work
+    ])
+end
+
 function aesthetic_mapping(::Type{LinesFill}, ::Normal, ::Normal)
     dictionary([
         1 => AesX,

src/algebra/layers.jl

@@ -432,7 +432,7 @@ function full_rescale(data, aes::Type{AesMarkerSize}, scale::ContinuousScale)
     values_to_markersizes(data, props.sizerange, scale.extrema)
 end
 
-full_rescale(data, aes::Type{<:Union{AesContourColor,AesABIntercept,AesABSlope}}, scale::ContinuousScale) = data # passthrough, this aes is a mock one anyway
+full_rescale(data, aes::Type{<:Union{AesContourColor,AesABIntercept,AesABSlope,AesVolumeColor}}, scale::ContinuousScale) = data # passthrough, this aes is a mock one anyway
 
 function values_to_markersizes(data, sizerange, extrema)
     # we scale the area linearly with the values

src/guides/legend.jl

@@ -384,7 +384,7 @@ function legend_elements(T::Type{Heatmap}, attributes, scale_args::MixedArgument
     )]
 end
 
-function legend_elements(T::Type{<:Union{HLines,VLines,Lines,LineSegments,Errorbars,Rangebars,Wireframe,ABLines,ECDFPlot}}, attributes, scale_args::MixedArguments)
+function legend_elements(T::Type{<:Union{HLines,VLines,Lines,LineSegments,Errorbars,Rangebars,Wireframe,ABLines,ECDFPlot,Stairs}}, attributes, scale_args::MixedArguments)
 
     is_vertical = T === VLines || (T <: Union{Errorbars,Rangebars} && _get(T, scale_args, attributes, :direction) === :y)
     # TODO: seems errorbars and rangebars are missing linestyle in Makie, once this is fixed, remove this

src/scales.jl

@@ -24,6 +24,7 @@ struct AesText <: Aesthetic end
 # maybe aesthetics that completely avoid scales 
 struct AesViolinSide <: Aesthetic end
 struct AesContourColor <: Aesthetic end # this is just so the third contour argument doesn't conflict with other things for now, it's complex to handle in its interplay with `color` and `levels`
+struct AesVolumeColor <: Aesthetic end # this is the fourth argument of volume
 struct AesPlaceholder <: Aesthetic end # choropleth for example takes as first arg only geometries which avoid scales, but for now we still have to give an aes to 1, so this can serve for that purpose
 struct AesABIntercept <: Aesthetic end
 struct AesABSlope <: Aesthetic end

src/transformations/stephistogram.jl

@@ -0,0 +1,28 @@
+Base.@kwdef struct StepHistogramAnalysis{D, B}
+    datalimits::D=automatic
+    bins::B=automatic
+    closed::Symbol=:left
+    normalization::Symbol=:none
+end
+
+function (h::StepHistogramAnalysis)(input::ProcessedLayer)
+    datalimits = h.datalimits === automatic ? defaultdatalimits(input.positional) : h.datalimits
+    options = valid_options(; datalimits, h.bins, h.closed, h.normalization)
+
+    output = map(input) do p, n
+        hist = _histogram(Tuple(p); pairs(n)..., pairs(options)...)
+        edges, weights = hist.edges, hist.weights
+        return (map(midpoints, edges)..., weights), (;)
+    end
+
+    N = length(input.positional)
+    @assert N == 1 "StepHistogram only supports 1D data"
+    label = h.normalization == :none ? "count" : string(h.normalization)
+    labels = set(output.labels, N+1 => label)
+    attributes = output.attributes
+    default_plottype = Stairs
+    plottype = Makie.plottype(input.plottype, default_plottype)
+    return ProcessedLayer(output; plottype, labels, attributes)
+end
+
+stephistogram(; options...) = transformation(StepHistogramAnalysis(; options...))