mirror of
https://gitlab.rlp.net/mobitar/ReCo.jl.git
synced 2024-12-21 00:51:21 +00:00
45 lines
1.2 KiB
Julia
45 lines
1.2 KiB
Julia
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using StaticArrays: SVector
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function project_to_unit_circle(x, l)
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φ = (x + l) * π / l
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return SVector(cos(φ), sin(φ))
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end
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function project_back_from_unit_circle(θ, l)
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x = θ * l / π - l
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return restrict_coordinate(x; l=l)
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end
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function center_of_mass(args)
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x_proj_sum = SVector(0, 0)
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y_proj_sum = SVector(0, 0)
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for p in args.particles
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x_proj_sum += project_to_unit_circle(p.c[1], args.l)
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y_proj_sum += project_to_unit_circle(p.c[2], args.l)
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end
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# Prevent for example atan(1e-16, 1e-15) != 0 with rounding
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digits = 5
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# No need for 1/N with atan
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# If proj is (0, 0) then COM is 0 or L or -L. Here, 0 is choosen with θ = π
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if (round(x_proj_sum[1]; digits=digits) == 0) &&
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(round(x_proj_sum[2]; digits=digits) == 0)
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x_θ = π
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else
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x_θ = atan(x_proj_sum[2], x_proj_sum[1])
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end
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if (round(y_proj_sum[1]; digits=digits) == 0) &&
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(round(y_proj_sum[2]; digits=digits) == 0)
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y_θ = π
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else
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y_θ = atan(y_proj_sum[2], y_proj_sum[1])
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end
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return SVector(
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project_back_from_unit_circle(x_θ, args.l),
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project_back_from_unit_circle(y_θ, args.l),
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)
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end
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