# Stipples using voronoi plot

**URL:** <https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745>\
**Category:** General Usage\
**Tags:** question\
**Created:** [May 26, 2024, 7:39am UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745 "2024-05-26T07:39:29Z")\
**Posts on this page:** 12\
**Page:** 1

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**Author:** ![Manasa\_S](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/manasa_s/32/209514_2.png) [@Manasa\_S](https://discourse.julialang.org/u/Manasa_S)\
**Post date:** [May 26, 2024, 7:39am UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745/1 "2024-05-26T07:39:29Z")

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Hi, I’m new to Julia and I’m trying to create a stippling based on voronoi diagrams. I’m using DelaunayTriangulation package. I’m confused on how to iterate for each point in the time series and generate a voronoi and extract its centroid positions and display the plot.

Does anyone have any insights, that would help me get the centroid points of each box defined at the graph.

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**Author:** ![kellertuer](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kellertuer/32/220707_2.png) [@kellertuer](https://discourse.julialang.org/u/kellertuer)\
**Post date:** [May 26, 2024, 11:06am UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745/2 "2024-05-26T11:06:30Z")

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Welcome to Julia Discourse! 👋

It would help, if you could provide what you tried so far and the first steps in code as a small example, see also

> [@Please read: make it easier to help you](https://discourse.julialang.org/t/please-read-make-it-easier-to-help-you/14757/1):
>
> Welcome to the Julia Discourse! We are enthusiastic about helping Julia programmers, both beginner and experienced. This public service announcement (PSA) outlines best practices when asking for help. Following these points makes it easier for us to help you and more likely you’ll get a prompt, useful answer. Keywords are highlighted to make it easier to refer to specific points. Choose a descriptive title that captures the key part of your question, eg “plots with multiple axes” instead of …

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**Author:** ![Manasa\_S](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/manasa_s/32/209514_2.png) [@Manasa\_S](https://discourse.julialang.org/u/Manasa_S)\
**Post date:** [May 26, 2024, 2:20pm UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745/3 "2024-05-26T14:20:50Z")

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Hi, Thank you for responding.

Here’s a snippet off my code:

```julia
using GLMakie

using DelaunayTriangulation

using GeometryBasics

using JSON

using StableRNGs

using Plots

data = JsonReader.read_json_data("data.json")

mean_data = data["mean"]

std_data = data["std"]

series_index = 1

axis, fig = PlotConfig.configure_plot("Uncertain time series", "years", "value")

mean_data_float32 = Float32.(mean_data[series_index])

std_data_float32 = Float32.(std_data[series_index])

time_range_float32 = Float32.(1:length(mean_data[series_index]))

mean_color = GLMakie.RGB(rand(), rand(), rand())

lines!(axis, time_range_float32, mean_data_float32, color = GLMakie.RGBA(mean_color, 0.8), label = "Mean")

# band!(axis, time_range_float32, mean_data_float32 .- std_data_float32, mean_data_float32 .+ std_data_float32, color = GLMakie.RGBA(mean_color, 0.6), label = "Error")

function boundary_points(x, y_lower, y_upper)

xs = Float32[]

ys = Float32[]

push!(xs, x - 0.5)

push!(ys, y_lower)

push!(xs, x + 0.5)

push!(ys, y_lower)

push!(xs, x + 0.5)

push!(ys, y_upper)

push!(xs, x - 0.5)

push!(ys, y_upper)

return xs, ys

end

rng = StableRNG(2)

all_xs = Float32[]

all_ys = Float32[]

for j in 1:20

x = time_range_float32[j]

y_mean = mean_data_float32[j]

y_lower = y_mean - std_data_float32[j]

y_upper = y_mean + std_data_float32[j]

num_points = max(3, Int(ceil(std_data_float32[j])))

xs, ys = boundary_points(x, y_lower, y_upper)

points = [(xs[k], ys[k]) for k in eachindex(xs, ys)]

tri = triangulate(points; rng)

refine!(tri; max_area = 1e-3, min_angle = 29.871, rng)

vorn = voronoi(tri)

smooth_vorn = centroidal_smooth(vorn; maxiters = 2500)

voronoiplot!(axis, smooth_vorn, show_generators = true, markersize = 4)

resize_to_layout!(fig)

end

```

Here i’m getting the boundaries of the error and constructing a voronoi. But i need them only to get the dots placement, Also it takes a lot of time to compute as well. Can you please suggest better ways to do.

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<div class="post-metadata">

**Author:** ![mkitti](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkitti/32/12459_2.png) [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Post date:** [May 26, 2024, 2:27pm UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745/4 "2024-05-26T14:27:31Z")

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Your code might be easier to read if you out them into a code block as follows.

````julia
```
# Your code here.
```

````

1. Could you explain why you are loading both Plots.jl and GLMakie.jl? I think you only need GLMakie.jl.
2. It might help to put mode of your code into a function, especially the for loop and loop comprehension.
3. If provide the type to the first argument of `ceil`, it will directly return that type without a need for casting.

```julia
num_points = max(3, ceil(Int, std_data_float32[j]))

```

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<div class="post-metadata">

**Author:** ![Manasa\_S](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/manasa_s/32/209514_2.png) [@Manasa\_S](https://discourse.julialang.org/u/Manasa_S)\
**Post date:** [May 26, 2024, 2:41pm UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745/5 "2024-05-26T14:41:08Z")

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Sorry that was something i was debugging on, yes you’re right I need just one of them. I have formatted the code as well. I want to get the positions of the centroids of the voronoi and plot them in a scatter plot

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**Author:** ![DanielVandH](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/danielvandh/32/31134_2.png) [@DanielVandH](https://discourse.julialang.org/u/DanielVandH)\
**Post date:** [May 26, 2024, 3:02pm UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745/6 "2024-05-26T15:02:32Z")

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Is this what you want?

```julia
using DelaunayTriangulation 
using CairoMakie
using StableRNGs
rng = StableRNG(123) 
points = tuple.(rand(rng, 50), rand(rng, 50))
tri = triangulate(points; rng)
vorn = voronoi(tri; rng)
svorn = centroidal_smooth(vorn; rng)
centroids = zeros(2, num_polygons(svorn))
for (j, i) in enumerate(each_polygon_index(svorn))
    centroids[:, j] .= DelaunayTriangulation.get_centroid(svorn, i)
end
scatter(centroids)

```

![u4gkKEP](https://global.discourse-cdn.com/julialang/original/3X/d/b/db0383e99272ff17b5f01c63de9e12af668bccdd.png)

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**Author:** ![DanielVandH](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/danielvandh/32/31134_2.png) [@DanielVandH](https://discourse.julialang.org/u/DanielVandH)\
**Post date:** [May 26, 2024, 3:06pm UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745/7 "2024-05-26T15:06:01Z")

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> [@Manasa\_S](#):
>
> Also it takes a lot of time to compute as well

Regarding speed… it should be pretty fast, but maybe I’ve been a bit inefficient in some areas. With `Float32` it’s possible you’re hitting some type instabilities since most of the testing is for `Float64` (I’ve tried to test for `Float32` where possible, but if I had to guess it’d be why).

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<div class="post-metadata">

**Author:** ![Manasa\_S](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/manasa_s/32/209514_2.png) [@Manasa\_S](https://discourse.julialang.org/u/Manasa_S)\
**Post date:** [May 26, 2024, 3:07pm UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745/8 "2024-05-26T15:07:20Z")

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HI, Yes I want to get the centroid positions. But I need to get the centroids for each positions in the error band area (the loop i have in the code `for j in 1: 20`, how can i store all the values and plot it?

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<div class="post-metadata">

**Author:** ![DanielVandH](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/danielvandh/32/31134_2.png) [@DanielVandH](https://discourse.julialang.org/u/DanielVandH)\
**Post date:** [May 26, 2024, 3:10pm UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745/9 "2024-05-26T15:10:32Z")

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You should be able to apply a similar idea as in the code I’ve given. `DelaunayTriangulation.get_centroid(smooth_vorn, i)` gives you the centroid for the `i`th polygon. You don’t need to use `voronoiplot!` to get these centroids.

So I imagine with your code just stop at `smooth_vorn`, use the loop I’ve shown you for computing the centroids of each polygon, and store it into some array like I’ve done. You can then plot via `scatter` as shown.

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<div class="post-metadata">

**Author:** ![Manasa\_S](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/manasa_s/32/209514_2.png) [@Manasa\_S](https://discourse.julialang.org/u/Manasa_S)\
**Post date:** [May 26, 2024, 3:11pm UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745/10 "2024-05-26T15:11:57Z")

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I will try this out. Thank you very much!! This really helps

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<div class="post-metadata">

**Author:** ![mkitti](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkitti/32/12459_2.png) [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Post date:** [May 26, 2024, 3:22pm UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745/11 "2024-05-26T15:22:19Z")

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Is this basically what the `boundary_points` function and the array comprehension are supposed to do?

```julia
julia> function boundary_points(x, y_lower, y_upper)
           xs = Float32[x-0.5, x+0.5, x+0.5, x-0.5]
           ys = Float32[y_lower, y_lower, y_upper, y_upper]
           return collect(zip(xs, ys))
       end
boundary_points (generic function with 1 method)

julia> boundary_points(2, 1, 3)
4-element Vector{Tuple{Float32, Float32}}:
 (1.5, 1.0)
 (2.5, 1.0)
 (2.5, 3.0)
 (1.5, 3.0)

```

It seems to me that then that `points` is just four points around a rectangle. Is it for those four points which you then triangulate?

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<div class="post-metadata">

**Author:** ![Manasa\_S](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/manasa_s/32/209514_2.png) [@Manasa\_S](https://discourse.julialang.org/u/Manasa_S)\
**Post date:** [May 26, 2024, 6:43pm UTC](https://discourse.julialang.org/t/stipples-using-voronoi-plot/114745/12 "2024-05-26T18:43:47Z")

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> [@mkitti](#):
>
> ```julia
> function boundary_points(x, y_lower, y_upper)
> xs = Float32[x-0.5, x+0.5, x+0.5, x-0.5]
> ys = Float32[y_lower, y_lower, y_upper, y_upper]
> return collect(zip(xs, ys))
> end
> 
> ```

Yes these points are to create a boundary for the triangulation and inside that voronoi should be constructed