# Adding N to each box
**URL:** https://discourse.julialang.org/t/adding-n-to-each-box/136688
**Category:** New to Julia
**Tags:** algebraofgraphics
**Created:** [April 12, 2026, 12:24pm UTC](https://discourse.julialang.org/t/adding-n-to-each-box/136688 "2026-04-12T12:24:56Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@mahmah](https://discourse.julialang.org/u/mahmah)
#### Post date: [April 12, 2026, 12:24pm UTC](https://discourse.julialang.org/t/adding-n-to-each-box/136688/1 "2026-04-12T12:24:56Z")
I’m trying to see the sample size in each boxplot using AoG. Looking for a robust solution that allows to easily see the number of elements in each box regardless of whether we use faceting, colors, dodge, e.g. Is this an impossible task?
---
### Author:  [@technocrat](https://discourse.julialang.org/u/technocrat)
#### Post date: [April 12, 2026, 5:49pm UTC](https://discourse.julialang.org/t/adding-n-to-each-box/136688/2 "2026-04-12T17:49:29Z")
You want the `categories` keyword to `draw()`
```julia-auto
using AlgebraOfGraphics
using CairoMakie
using Random
Random.seed!(42)
# Data setup
counts = Dict("A" => 30, "C" => 22, "D" => 45)
groups = vcat([fill(g, counts[g]) for g in ["A", "C", "D"]]...)
values = vcat(
randn(counts["A"]) .* 1.2 .+ 1.0,
randn(counts["C"]) .* 0.8 .+ 3.5,
randn(counts["D"]) .* 1.5 .+ 4.5,
)
df = (; group = groups, value = values)
spec = data(df) * mapping(:group, :value) * visual(BoxPlot)
f = Figure(size = (1200, 400))
# Helper to create the pair mappings for AoG scales
# Returns something like: ["A" => "A\nN=30", ...]
function label_with_n(keys)
return [k => "$k\nN=$(counts[k])" for k in keys]
end
# ae1: Default order (Alphabetical)
ae1 = draw!(f[1, 1], spec, scales(X = (; categories = label_with_n(["A", "C", "D"]))))
# ae2: Custom order ("D", "A", "C")
ae2 = draw!(f[1, 2], spec, scales(X = (; categories = label_with_n(["D", "A", "C"]))))
# ae3: Using your[1] explicit dictionary-style mapping
# Note: AoG expects an AbstractVector of Pairs for the categories scale
ae3_labels = ["A" => "A\nN=$(counts["A"])", "C" => "C\nN=$(counts["C"])", "D" => "D\nN=$(counts["D"])"]
ae3 = draw!(f[1, 3], spec, scales(X = (; categories = ae3_labels)))
f
```
* * *
[1] Yes, I got help with this. I took a swing at it, missed, thought about it, and properly presented the question to Gemini.
---
### Author:  [@mahmah](https://discourse.julialang.org/u/mahmah)
#### Post date: [April 12, 2026, 6:09pm UTC](https://discourse.julialang.org/t/adding-n-to-each-box/136688/3 "2026-04-12T18:09:32Z")
Thanks! This might help, but what if we have this?
Also, I guess the point of AoG is that there should be no need to write factor levels, right?
---
### Author:  [@jules](https://discourse.julialang.org/u/jules)
#### Post date: [April 12, 2026, 7:20pm UTC](https://discourse.julialang.org/t/adding-n-to-each-box/136688/4 "2026-04-12T19:20:55Z")
I had a PR for aggregations [Add flexible `aggregate` analysis layer by jkrumbiegel · Pull Request #696 · MakieOrg/AlgebraOfGraphics.jl · GitHub](https://github.com/MakieOrg/AlgebraOfGraphics.jl/pull/696) but after merging it into a 0.12 branch already, I didn’t use it after all. Too many edge cases and not enough flexibility after all, I found. Until I can come up with a better solution, I decided to leave aggregations to data wrangling packages, but your example is a good one why it can be annoying. As you say, you’d like this to work with `color` grouping, `dodge`, whatever. Making a custom AoG analysis type just for this would work but is a bit heavy-handed. Also this one only works with a small fix to the dodging resolution mechanism in AoG I’ll need to make (another annoyance here is that boxplot needs `dodge` while `Text` needs the generic `dodge_x`):
```julia
using AlgebraOfGraphics, CairoMakie
using AlgebraOfGraphics: transformation, ProcessedLayer, Verbatim
struct GroupCount end
function (::GroupCount)(input::ProcessedLayer)
output = map(input) do p, n
xs, ys = p
uxs = sort(unique(xs))
counts = [count(==(x), xs) for x in uxs]
maxys = [maximum(ys[xs .== x]) for x in uxs]
return (uxs, maxys), Dict(:text => [Verbatim("n=$c") for c in counts])
end
return ProcessedLayer(output; plottype = Makie.Text)
end
groupcount() = transformation(GroupCount())
df = (;
group = [fill("A", 10); fill("A", 20); fill("B", 30); fill("B", 50)],
color = [fill("x", 10); fill("y", 20); fill("x", 30); fill("y", 50)],
value = [randn(10) .+ 1; randn(20) .+ 2; randn(30) .+ 2; randn(50) .+ 3],
)
draw(data(df) * mapping(:group, :value, color = :color) *
(visual(BoxPlot) * mapping(dodge = :color) + groupcount() * mapping(dodge_x = :color)))
```
---
### Author:  [@technocrat](https://discourse.julialang.org/u/technocrat)
#### Post date: [April 12, 2026, 11:19pm UTC](https://discourse.julialang.org/t/adding-n-to-each-box/136688/5 "2026-04-12T23:19:17Z")
@jules solution seems to address this, except for the notch which can be added with `show-notch = true`, as an alternative to using the `categories` keyword. Not sure what you mean by writing factor levels.
---
### Author:  [@mahmah](https://discourse.julialang.org/u/mahmah)
#### Post date: [April 13, 2026, 7:35am UTC](https://discourse.julialang.org/t/adding-n-to-each-box/136688/6 "2026-04-13T07:35:05Z")
Thanks, wow! I tried it with the latest version of AoG but I get this error:
```julia-auto
ERROR: Dictionaries.IndexError("Dictionary does not contain index: text")
Stacktrace:
[1] getindex
@ ~/.julia/packages/Dictionaries/P05gc/src/AbstractDictionary.jl:46 [inlined]
[2] (::AlgebraOfGraphics.var"#to_entry##8#to_entry##9"{Dictionaries.Dictionary{…}, Dictionaries.Dictionary{…}, Dictionaries.Dictionary{…}, Dictionaries.Dictionary{…}, Symbol, Type{…}, Type{…}})(::Pair{Symbol, Vector{…}})
@ AlgebraOfGraphics ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/algebra/layers.jl:546
[3] map!(f::AlgebraOfGraphics.var"#to_entry##8#to_entry##9"{…}, out::Dictionaries.Dictionary{…}, d::Dictionaries.PairDictionary{…})
@ Dictionaries ~/.julia/packages/Dictionaries/P05gc/src/map.jl:66
[4] map
@ ~/.julia/packages/Dictionaries/P05gc/src/map.jl:106 [inlined]
[5] to_entry(P::Type, p::ProcessedLayer, categoricalscales::Dictionaries.Dictionary{Type{…}, Dictionaries.Dictionary{…}}, continuousscales::Dictionaries.Dictionary{Type{…}, Dictionaries.Dictionary{…}})
@ AlgebraOfGraphics ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/algebra/layers.jl:545
[6] to_entry(p::ProcessedLayer, categoricalscales::Dictionaries.Dictionary{Type{…}, Dictionaries.Dictionary{…}}, continuousscales::Dictionaries.Dictionary{Type{…}, Dictionaries.Dictionary{…}})
@ AlgebraOfGraphics ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/algebra/layers.jl:502
[7] #compute_entries_continuousscales##6
@ ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/algebra/layers.jl:185 [inlined]
[8] iterate
@ ./generator.jl:48 [inlined]
[9] collect_to!
@ ./array.jl:848 [inlined]
[10] collect_to_with_first!
@ ./array.jl:826 [inlined]
[11] _collect(c::Vector{ProcessedLayer}, itr::Base.Generator{Vector{…}, AlgebraOfGraphics.var"#compute_entries_continuousscales##6#compute_entries_continuousscales##7"{…}}, ::Base.EltypeUnknown, isz::Base.HasShape{1})
@ Base ./array.jl:820
[12] collect_similar
@ ./array.jl:732 [inlined]
[13] map
@ ./abstractarray.jl:3372 [inlined]
[14] #compute_entries_continuousscales##4
@ ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/algebra/layers.jl:184 [inlined]
[15] #Generator##0
@ ./generator.jl:37 [inlined]
[16] iterate
@ ./generator.jl:48 [inlined]
[17] collect(itr::Base.Generator{Base.Iterators.Zip{Tuple{…}}, Base.var"#Generator##0#Generator##1"{AlgebraOfGraphics.var"#compute_entries_continuousscales##4#compute_entries_continuousscales##5"{…}}})
@ Base ./array.jl:790
[18] map
@ ./abstractarray.jl:3526 [inlined]
[19] compute_entries_continuousscales(pls_grid::Matrix{Vector{…}}, categoricalscales::Dictionaries.Dictionary{Type{…}, Dictionaries.Dictionary{…}}, scale_props::Dictionaries.Dictionary{Type{…}, Dictionaries.Dictionary{…}})
@ AlgebraOfGraphics ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/algebra/layers.jl:183
[20] compute_axes_grid(d::Layers, scales::AlgebraOfGraphics.Scales; axis::Dictionaries.Dictionary{Symbol, Any})
@ AlgebraOfGraphics ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/algebra/layers.jl:349
[21] compute_axes_grid
@ ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/algebra/layers.jl:314 [inlined]
[22] _draw(d::Layers, scales::AlgebraOfGraphics.Scales; axis::Dictionaries.Dictionary{…}, figure::Dictionaries.Dictionary{…}, facet::Dictionaries.Dictionary{…}, legend::Dictionaries.Dictionary{…}, colorbar::Dictionaries.Dictionary{…})
@ AlgebraOfGraphics ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/draw.jl:186
[23] _draw
@ ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/draw.jl:181 [inlined]
[24] draw(d::Layers, scales::AlgebraOfGraphics.Scales; axis::@NamedTuple{}, figure::@NamedTuple{}, facet::@NamedTuple{}, legend::@NamedTuple{}, colorbar::@NamedTuple{}, palette::Nothing)
@ AlgebraOfGraphics ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/draw.jl:112
[25] draw
@ ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/draw.jl:100 [inlined]
[26] draw(d::Layers)
@ AlgebraOfGraphics ~/.julia/packages/AlgebraOfGraphics/T2K4z/src/draw.jl:100
[27] top-level scope
@ REPL[29]:1
[28] top-level scope
@ REPL:1
Some type information was truncated. Use `show(err)` to see complete types.
```
---
### Author:  [@mahmah](https://discourse.julialang.org/u/mahmah)
#### Post date: [April 13, 2026, 7:36am UTC](https://discourse.julialang.org/t/adding-n-to-each-box/136688/7 "2026-04-13T07:36:35Z")
In the plot made by jules, A and B would be factors (or groups) and x and y their levels.
---
### Author:  [@jules](https://discourse.julialang.org/u/jules)
#### Post date: [April 13, 2026, 7:44am UTC](https://discourse.julialang.org/t/adding-n-to-each-box/136688/8 "2026-04-13T07:44:24Z")
> [@jules](#):
>
> Also this one only works with a small fix to the dodging resolution mechanism in AoG I’ll need to make
That’s why I wrote the above 🙂
One thing I thought about adding is that one can use the `dodge_x` thing also for the recipes that already have their own `dodge` and it would work as long as the `dodge` is actually in `x`. That would make it easier to layer `dodge`-having recipes with those that don’t.
---
### Author:  [@mahmah](https://discourse.julialang.org/u/mahmah)
#### Post date: [April 13, 2026, 1:21pm UTC](https://discourse.julialang.org/t/adding-n-to-each-box/136688/9 "2026-04-13T13:21:54Z")
Oh sorry! Anyway, if you can let me know when this can be used at least from a devel version, it would be great! 😊
In the meantime I’ll try to study the solution.