RectilinearGrid: Implement multidimensional indexing (#669)

JuliaGeometry · Dec 26, 2023 · 9e99530 · 9e99530
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diff --git a/src/mesh/rectilineargrid.jl b/src/mesh/rectilineargrid.jl
@@ -56,3 +56,11 @@ function centroid(g::RectilinearGrid, ind::Int)
   p2 = vertex(g, ijk .+ 1)
   Point((coordinates(p1) + coordinates(p2)) / 2)
 end
+
+function Base.getindex(g::RectilinearGrid{Dim}, I::CartesianIndices{Dim}) where {Dim}
+  dims = size(I)
+  start = Tuple(first(I))
+  stop = Tuple(last(I)) .+ 1
+  xyz = ntuple(i -> g.xyz[i][start[i]:stop[i]], Dim)
+  RectilinearGrid(xyz, GridTopology(dims))
+end
diff --git a/test/mesh.jl b/test/mesh.jl
@@ -238,6 +238,14 @@
     @test vertex(grid, nvertices(grid)) == vertex(grid, size(grid) .+ 1)
     @test grid[1, 1] == grid[1]
     @test grid[5, 5] == grid[25]
+    sub = grid[2:4, 3:5]
+    @test size(sub) == (3, 3)
+    @test minimum(sub) == P2(0.2, 0.3)
+    @test maximum(sub) == P2(0.8, 1.0)
+    sub = grid[2, 3:5]
+    @test size(sub) == (1, 3)
+    @test minimum(sub) == P2(0.2, 0.3)
+    @test maximum(sub) == P2(0.4, 1.0)
     @test Meshes.xyz(grid) == (x, y)
     @test Meshes.XYZ(grid) == (repeat(x, 1, 6), repeat(y', 6, 1))