File:Green's function animation.gif
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Size of this preview: 600 × 600 pixels. Other resolutions: 240 × 240 pixels | 480 × 480 pixels | 640 × 640 pixels.
Original file (640 × 640 pixels, file size: 1.69 MB, MIME type: image/gif, looped, 202 frames, 20 s)
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Summary[edit]
DescriptionGreen's function animation.gif |
English: An intuitive animation that shows how Green's functions that solve a differential equation subject to a point-like source can be superposed to solve it subject to an arbitrary source. |
Date | |
Source | Own work |
Author | Hersle |
Julia code[edit]
using LinearAlgebra using Plots using Printf function solve(f; x1=0, x2=1) N = length(f) x = Array(range(x1, x2, length=N)) h = x[2] - x[1] diag = fill(+2/h^2, N-2) semidiag = fill(-1/h^2, N-3) L = Tridiagonal(semidiag, diag, semidiag) u = L \ f[2:end-1] u = cat([0], u, [0], dims=1) return x, u end function animate() # Store all Green's function solutions N = 101 U = zeros(N, N) p = plot() for i in 1:N f = [i == j ? 1 : 0 for j in 1:N] x, u = solve(f) U[i,:] = u plot!(p, u) end # Solve a real problem f1 = exp.(-(x.-0.5).^2 / (2*0.01)) x, u1 = solve(f1) u = zeros(N) barw = x[2]-x[1] # plot bars with no gap between them anim = @animate for i in 1:N y = @sprintf("%.2f", (i-1) / (N-1)) # as string f2 = [i == j ? 1 : 0 for j in 1:N] x, u2 = solve(f2) u += u2 * f1[i] colors = [i == j ? :black : :red for j in 1:N] # for some reason, only (1599, 1600) gives a height that is divisible by 2 during mp4 generation plot(layout=(2, 2), size=(1599, 1600), xlims=(0,1), xticks=([0, 0.5, 1], ["\$0\$", "\$x\$", "\$1\$"]), yticks=nothing, bar_width=barw, titlefontsize=40, tickfontsize=40, framestyle=:box, grid=false, legend=nothing, margin=10Plots.mm, top_margin=0Plots.mm) # Plot point-source and Green's function solution bar!(subplot=1, x[i:i], f2[i:i], color=:green, linecolor=:green, bar_width=barw, ylims=(0, 1.10), title="\$\\delta(x-$y)\$") bar!(subplot=2, x, u2, color=:darkgreen, linecolor=:darkgreen, bar_width=barw, ylims=(0, 0.02), title="\$G(x,$y)\$") # Plot full source and full solution bar!(subplot=3, x[1:i], f1[1:i], color=:blue, linecolor=:blue, bar_width=barw, ylims=(0, 1.10), title="\$ \\hat{L}\\,(x) u(x) = f(x < $y) \$") bar!(subplot=3, x[i+1:end], f1[i+1:end], color=:lightgrey, linecolor=:lightgrey, bar_width=barw, ylims=(0, 1.10)) bar!(subplot=4, x, u1, color=:lightgrey, linecolor=:lightgrey, bar_width=barw, ylims=(0, 0.06)) bar!(subplot=4, x, u, color=:darkblue, linecolor=:darkblue, bar_width=barw, ylims=(0, 0.06), title="\$ u(x) = {\\int}_{0}^{$y} \\! f(x') \\, G(x,x') \\, \\mathrm{d} x' \$") end mp4(anim, "green.mp4", fps=5) run(`ffmpeg -i green.mp4 -vf "fps=10,scale=640:640:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" -loop 0 green.gif`) end animate()
Licensing[edit]
I, the copyright holder of this work, hereby publish it under the following license:
This file is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.
- You are free:
- to share – to copy, distribute and transmit the work
- to remix – to adapt the work
- Under the following conditions:
- attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
- share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.
File history
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Date/Time | Thumbnail | Dimensions | User | Comment | |
---|---|---|---|---|---|
current | 21:27, 21 December 2022 | 640 × 640 (1.69 MB) | Hersle (talk | contribs) | Show changing source values | |
17:36, 16 June 2021 | 640 × 640 (754 KB) | Hersle (talk | contribs) | Reduced size to enable automatic animation | ||
12:48, 16 June 2021 | 960 × 961 (1.3 MB) | Hersle (talk | contribs) | Cross-wiki upload from en.wikipedia.org |
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