Skip to content

[WIP] Sampling points from geometry #184

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 2 commits into
base: main
Choose a base branch
from
Open

[WIP] Sampling points from geometry #184

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
e26c94e
First semi working version
asinghvi17 Jul 21, 2024
3d8a4d3
Remove old code
asinghvi17 Jul 26, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 2 additions & 0 deletions Project.toml
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
SortTileRecursiveTree = "746ee33f-1797-42c2-866d-db2fce69d14d"
Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
StatsBase = "2913bbd2-ae8a-5f71-8c99-4fb6c76f3a91"
Tables = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"

[weakdeps]
Expand All @@ -35,6 +36,7 @@ LinearAlgebra = "1"
Proj = "1"
SortTileRecursiveTree = "0.1"
Statistics = "1"
StatsBase = "0.34"
Tables = "1"
julia = "1.9"

Expand Down
2 changes: 2 additions & 0 deletions src/GeometryOps.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ using GeoInterface
using GeometryBasics
import Tables
using LinearAlgebra, Statistics
import StatsBase
import GeometryBasics.StaticArrays
import ExactPredicates
import Base.@kwdef
Expand Down Expand Up @@ -47,6 +48,7 @@ include("methods/geom_relations/intersects.jl")
include("methods/geom_relations/overlaps.jl")
include("methods/geom_relations/touches.jl")
include("methods/geom_relations/within.jl")
include("methods/sample.jl")
include("methods/orientation.jl")
include("methods/polygonize.jl")

Expand Down
61 changes: 61 additions & 0 deletions src/methods/sample.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,61 @@
#=
# Sample

```@example sample
import GeoInterface as GI, GeometryOps as GO
p1 = GI.Polygon([[[-55965.680060140774, -31588.16072168928], [-55956.50771556479, -31478.09258677756], [-31577.548550575284, -6897.015828572996], [-15286.184961223798, -15386.952072224134], [-9074.387601621409, -27468.20712382156], [-8183.4538916097845, -31040.003969070774], [-27011.85123029944, -38229.02388009402], [-54954.72822634951, -32258.9734800704], [-55965.680060140774, -31588.16072168928]]])
Copy link
Member

@rafaqz rafaqz Jul 25, 2024

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Can we use tuple points in examples? (To teach good habits)

points = GO.sample(p1, 100)
using CairoMakie
f, a, p = poly(p1)
scatter!(a, points)
f
```

=#

export sample, UniformSampling

struct UniformSampling
end

application_level(::UniformSampling) = TraitTarget(GI.MultiPolygonTrait(), GI.MultiLineStringTrait(), GI.MultiPointTrait(), GI.PolygonTrait(), GI.LineStringTrait())

function sample(geom, n::Int)
return sample(UniformSampling(), geom, n)
end

function sample(alg, geom, n)
return apply(x -> _sample(alg, GI.trait(x), x, n), application_level(alg), geom)
Copy link
Member

@rafaqz rafaqz Jul 25, 2024

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should we even use apply for this? What happens to a feature collection or DataFrame?

My intuitive understanding would be to sample points from all geometries of all of the features weighted by area.

Copy link
Member Author

@asinghvi17 asinghvi17 Jul 26, 2024

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

At this point each feature will be sampled independently, so it's a dataframe to dataframe transfer. Since everything else also works the same way (centroid etc) I think this is at least consistent?

Am open to discussion though, not sure how people generally use this stuff.

Copy link
Member Author

@asinghvi17 asinghvi17 Jul 26, 2024

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

GeoPandas samples per geometry, and returns a multipoint:
https://geopandas.org/en/stable/docs/reference/api/geopandas.GeoSeries.sample_points.html

GO.centroid does return a single point even if you pass in a feature collection or table. (There's an issue with the Natural Earth north Korea geometry as well :D)

Copy link
Member Author

@asinghvi17 asinghvi17 Jul 26, 2024

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Aah, yeah apply won't work here since it will try to reconstruct.

I guess this is a good time to figure out the generic apply iterator thing?

end

function _sample(alg::UniformSampling, ::Union{GI.PolygonTrait, GI.MultiPolygonTrait}, geom, n)
(; X, Y) = GI.extent(geom)
points = fill((0.0, 0.0), n)
i = 1
while i <= n
x = rand() * (X[2] - X[1]) + X[1]
y = rand() * (Y[2] - Y[1]) + Y[1]
if contains(geom, (x, y))
points[i] = (x, y)
i += 1
end
end
return points
end

function _sample(alg::UniformSampling, ::GI.LineStringTrait, geom, n)
edges = to_edges(geom)
edge_lengths = map(splat(distance), edges)
# normalize the vector
edge_lengths .= edge_lengths
edge_probabilities = edge_lengths ./ sum(edge_lengths)
edge_idxs = 1:length(edges)
return map(1:n) do _
edge_idx = sample(edge_idxs, edge_probabilities)
x1, y1 = edges[edge_idx][1]
x2, y2 = edges[edge_idx][2]
distance = edge_lengths[edge_idx]
t = rand() * distance
(x1 + t * (x2 - x1), y1 + t * (y2 - y1))
end
Comment on lines +52 to +59
Copy link
Member Author

@asinghvi17 asinghvi17 Jul 26, 2024

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

The better way to do this is probably to define a vector of points, and then set indices in that vector. Could also open the way for multithreading in the future.

end