hexbin

Makie.hexbin Function

hexbin(xs, ys; kwargs...)

Plots a heatmap with hexagonal bins for the observations xs and ys.

Plot type

The plot type alias for the hexbin function is Hexbin.

source

Examples

Setting the number of bins

Setting bins to an integer sets the number of bins to this value for both x and y. The minimum number of bins in one dimension is 2.

using CairoMakie
using Random
Random.seed!(1234)

f = Figure(size = (800, 800))

x = rand(300)
y = rand(300)

for i in 2:5
    ax = Axis(f[fldmod1(i-1, 2)...], title = "bins = $i", aspect = DataAspect())
    hexbin!(ax, x, y, bins = i)
    wireframe!(ax, Rect2f(Point2f.(x, y)), color = :red)
    scatter!(ax, x, y, color = :red, markersize = 5)
end

f

You can also pass a tuple of integers to control x and y separately.

using CairoMakie
using Random
Random.seed!(1234)

f = Figure(size = (800, 800))

x = rand(300)
y = rand(300)

for i in 2:5
    ax = Axis(f[fldmod1(i-1, 2)...], title = "bins = (3, $i)", aspect = DataAspect())
    hexbin!(ax, x, y, bins = (3, i))
    wireframe!(ax, Rect2f(Point2f.(x, y)), color = :red)
    scatter!(ax, x, y, color = :red, markersize = 5)
end

f

Setting the size of cells

You can also control the cell size directly by setting the cellsize keyword. In this case, the bins setting is ignored.

The height of a hexagon is larger than its width. This is why setting the same size for x and y will result in uneven hexagons.

using CairoMakie
using Random
Random.seed!(1234)

f = Figure(size = (800, 800))

x = rand(300)
y = rand(300)

for (i, cellsize) in enumerate([0.1, 0.15, 0.2, 0.25])
    ax = Axis(f[fldmod1(i, 2)...], title = "cellsize = ($cellsize, $cellsize)", aspect = DataAspect())
    hexbin!(ax, x, y, cellsize = (cellsize, cellsize))
    wireframe!(ax, Rect2f(Point2f.(x, y)), color = :red)
    scatter!(ax, x, y, color = :red, markersize = 5)
end

f

To get evenly sized hexagons, set the cell size to a single number. This number defines the cell width, the height will be computed as 2 * step_x / sqrt(3). Note that the visual appearance of the hexagons will only be even if the x and y axis have the same scaling, which is why we use aspect = DataAspect() in these examples.

using CairoMakie
using Random
Random.seed!(1234)

f = Figure(size = (800, 800))

x = rand(300)
y = rand(300)

for (i, cellsize) in enumerate([0.1, 0.15, 0.2, 0.25])
    ax = Axis(f[fldmod1(i, 2)...], title = "cellsize = $cellsize", aspect = DataAspect())
    hexbin!(ax, x, y, cellsize = cellsize)
    wireframe!(ax, Rect2f(Point2f.(x, y)), color = :red)
    scatter!(ax, x, y, color = :red, markersize = 5)
end

f

Hiding hexagons with low counts

All hexagons with a count lower than threshold will be removed:

using CairoMakie
using Random
Random.seed!(1234)

f = Figure(size = (800, 800))

x = randn(100000)
y = randn(100000)

for (i, threshold) in enumerate([1, 10, 100, 500])
    ax = Axis(f[fldmod1(i, 2)...], title = "threshold = $threshold", aspect = DataAspect())
    hexbin!(ax, x, y, cellsize = 0.4, threshold = threshold)
end
f

Changing the scale of the number of observations in a bin

You can pass a scale function to via the colorscale keyword, which will be applied to the bin counts before plotting.

using CairoMakie
using Random
Random.seed!(1234)

x = randn(100000)
y = randn(100000)

f = Figure()
hexbin(f[1, 1], x, y, bins = 40,
    axis = (aspect = DataAspect(), title = "colorscale = identity"))
hexbin(f[1, 2], x, y, bins = 40, colorscale=log10,
    axis = (aspect = DataAspect(), title = "colorscale = log10"))
f

Showing zero count hexagons

By setting threshold = 0, all hexagons that fit into the limits of the input data are shown. In this example, we add a transparent color to the start of the colormap and stroke each hexagon so the empty hexagons are visible but not too distracting.

using CairoMakie
using DelimitedFiles


a = map(Point2f, eachrow(readdlm(assetpath("airportlocations.csv"))))

f, ax, hb = hexbin(a,
    cellsize = 6,
    axis = (; aspect = DataAspect()),
    threshold = 0,
    colormap = [Makie.to_color(:transparent); Makie.to_colormap(:viridis)],
    strokewidth = 0.5,
    strokecolor = :gray50,
    colorscale = Makie.pseudolog10)

tightlimits!(ax)

Colorbar(f[1, 2], hb,
    label = "Number of airports",
    height = Relative(0.5)
)
f

Applying weights to observations

using CairoMakie

using Random
Random.seed!(1234)

f = Figure(size = (800, 800))

x = 1:100
y = 1:100
points = vec(Point2f.(x, y'))

weights = [nothing, rand(length(points)), Makie.StatsBase.eweights(length(points), 0.005), Makie.StatsBase.weights(randn(length(points)))]
weight_labels = ["No weights", "Vector{<: Real}", "Exponential weights (StatsBase.eweights)", "StatesBase.weights(randn(...))"]

for (i, (weight, title)) in enumerate(zip(weights, weight_labels))
    ax = Axis(f[fldmod1(i, 2)...], title = title, aspect = DataAspect())
    hexbin!(ax, points; weights = weight)
    autolimits!(ax)
end

f

Attributes

alpha

Defaults to 1.0

The alpha value of the colormap or color attribute. Multiple alphas like in plot(alpha=0.2, color=(:red, 0.5), will get multiplied.

bins

Defaults to 20

Sets the number of bins in the x and y direction. They can be set separately with a tuple or together with an integer.

cellsize

Defaults to nothing

Sets the size of hexagons. The width and height can be set separately with a tuple or together with a real number.

clip_planes

Defaults to @inherit clip_planes automatic

Clip planes offer a way to do clipping in 3D space. You can set a Vector of up to 8 Plane3f planes here, behind which plots will be clipped (i.e. become invisible). By default clip planes are inherited from the parent plot or scene. You can remove parent clip_planes by passing Plane3f[].

colormap

Defaults to @inherit colormap :viridis

Sets the colormap that is sampled for numeric colors. PlotUtils.cgrad(...), Makie.Reverse(any_colormap) can be used as well, or any symbol from ColorBrewer or PlotUtils. To see all available color gradients, you can call Makie.available_gradients().

colorrange

Defaults to automatic

The values representing the start and end points of colormap.

colorscale

Defaults to identity

The color transform function. Can be any function, but only works well together with Colorbar for identity, log, log2, log10, sqrt, logit, Makie.pseudolog10, Makie.Symlog10, Makie.AsinhScale, Makie.SinhScale, Makie.LogScale, Makie.LuptonAsinhScale, and Makie.PowerScale.

depth_shift

Defaults to 0.0

Adjusts the depth value of a plot after all other transformations, i.e. in clip space, where -1 <= depth <= 1. This only applies to GLMakie and WGLMakie and can be used to adjust render order (like a tunable overdraw).

fxaa

Defaults to false

Adjusts whether the plot is rendered with fxaa (fast approximate anti-aliasing, GLMakie only). Note that some plots implement a better native anti-aliasing solution (scatter, text, lines). For them fxaa = true generally lowers quality. Plots that show smoothly interpolated data (e.g. image, surface) may also degrade in quality as fxaa = true can cause blurring.

highclip

Defaults to automatic

The color for any value above the colorrange.

inspectable

Defaults to @inherit inspectable

Sets whether this plot should be seen by DataInspector. The default depends on the theme of the parent scene.

inspector_clear

Defaults to automatic

Sets a callback function (inspector, plot) -> ... for cleaning up custom indicators in DataInspector.

inspector_hover

Defaults to automatic

Sets a callback function (inspector, plot, index) -> ... which replaces the default show_data methods.

inspector_label

Defaults to automatic

Sets a callback function (plot, index, position) -> string which replaces the default label generated by DataInspector.

lowclip

Defaults to automatic

The color for any value below the colorrange.

model

Defaults to automatic

Sets a model matrix for the plot. This overrides adjustments made with translate!, rotate! and scale!.

nan_color

Defaults to :transparent

The color for NaN values.

overdraw

Defaults to false

Controls if the plot will draw over other plots. This specifically means ignoring depth checks in GL backends

space

Defaults to :data

Sets the transformation space for box encompassing the plot. See Makie.spaces() for possible inputs.

ssao

Defaults to false

Adjusts whether the plot is rendered with ssao (screen space ambient occlusion). Note that this only makes sense in 3D plots and is only applicable with fxaa = true.

strokecolor

Defaults to :black

Sets the color of hexagon outlines. Requires strokewidth > 0.

strokewidth

Defaults to 0

Sets the width of hexagon outlines.

threshold

Defaults to 1

The minimal number of observations in the bin for it to be shown. If 0, all zero-count hexagons fitting into the data limits will be shown.

transformation

Defaults to :automatic

Controls the inheritance or directly sets the transformations of a plot. Transformations include the transform function and model matrix as generated by translate!(...), scale!(...) and rotate!(...). They can be set directly by passing a Transformation() object or inherited from the parent plot or scene. Inheritance options include:

• :automatic: Inherit transformations if the parent and child space is compatible

• :inherit: Inherit transformations

• :inherit_model: Inherit only model transformations

• :inherit_transform_func: Inherit only the transform function

• :nothing: Inherit neither, fully disconnecting the child's transformations from the parent

Another option is to pass arguments to the transform!() function which then get applied to the plot. For example transformation = (:xz, 1.0) which rotates the xy plane to the xz plane and translates by 1.0. For this inheritance defaults to :automatic but can also be set through e.g. (:nothing, (:xz, 1.0)).

transparency

Defaults to false

Adjusts how the plot deals with transparency. In GLMakie transparency = true results in using Order Independent Transparency.

visible

Defaults to true

Controls whether the plot gets rendered or not.

weights

Defaults to nothing

Weights for each observation. Can be nothing (each observation carries weight 1), any AbstractVector{<: Real} or any StatsBase.AbstractWeights.