From 850e1f4668ac06fe0473f3110ce5edd105ad85d6 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Jon=C3=A1=C5=A1=20Koziorek?= <73384756+JonasKoziorek@users.noreply.github.com> Date: Fri, 7 Jun 2024 14:29:14 +0200 Subject: [PATCH] docs fix (#333) --- docs/src/periodicity.md | 2 +- src/periodicity/davidchacklai.jl | 15 +++++++++------ 2 files changed, 10 insertions(+), 7 deletions(-) diff --git a/docs/src/periodicity.md b/docs/src/periodicity.md index bd9416b8..f83b6eac 100644 --- a/docs/src/periodicity.md +++ b/docs/src/periodicity.md @@ -169,7 +169,7 @@ davidchacklai #### Logistic Map example The idea of periodic orbits can be illustrated easily on 1D maps. Finding all periodic orbits of period -$n$ is equivalent to finding all points $x$ such that $f^{n}(x)=x$, where $f^{n}$ is $n$-th composition of $f$. Hence, solving $f^{n}(x)-x=0$ yields such points. However, this is impossible analytically. +$n$ is equivalent to finding all points $x$ such that $f^{n}(x)=x$, where $f^{n}$ is $n$-th composition of $f$. Hence, solving $f^{n}(x)-x=0$ yields such points. However, this is often impossible analytically. Let's see how `davidchacklai` deals with it: First let's start with finding first $9$ periodic orbits of the logistic map for parameter $3.72$. diff --git a/src/periodicity/davidchacklai.jl b/src/periodicity/davidchacklai.jl index a69bc475..ac4cb059 100644 --- a/src/periodicity/davidchacklai.jl +++ b/src/periodicity/davidchacklai.jl @@ -25,7 +25,7 @@ periodic orbits will be used to detect periodic orbits of order `m+1` to `n`. is an `n`-periodic point. * `abstol = 1e-8`: A detected periodic point isn't stored if it is in `abstol` neighborhood of some previously detected point. Distance is measured by - euclidian norm. If you are getting duplicate periodic points, decrease this value. + euclidian norm. If you are getting duplicate periodic points, increase this value. ## Description @@ -37,7 +37,7 @@ by turning fixed points of the original map `ds` to stable ones, through the transformation ```math \\mathbf{x}_{n+1} = \\mathbf{x}_{n} + -[\\beta |g(\\mathbf{x}_{n}| C^{T} - J(\\mathbf{x}_{n})]^{-1} g(\\mathbf{x}_{n}) +[\\beta |g(\\mathbf{x}_{n})| C^{T} - J(\\mathbf{x}_{n})]^{-1} g(\\mathbf{x}_{n}) ``` where ```math @@ -46,7 +46,7 @@ g(\\mathbf{x}_{n}) = f^{n}(\\mathbf{x}_{n}) - \\mathbf{x}_{n} and ```math J(\\mathbf{x}_{n}) = \\frac{\\partial g(\\mathbf{x}_{n})}{\\partial \\mathbf{x}_{n}} -```` +``` The main difference between Schmelcher & Diakonos[Schmelcher1997](@cite) and Davidchack & Lai[Davidchack1999](@cite) is that the latter uses periodic points of @@ -58,9 +58,12 @@ while `davidchacklai` detects periodic points of all orders up to `n`. ## Important note For low periods `n` circa less than 6, you should select `m = n` otherwise the algorithm -detect periodic orbits correctly. For higher periods, you can select `m` as 6. -You can use initial grid of points for `ics`. Increase `m` in case the orbits are -not being detected correctly. +won't detect periodic orbits correctly. For higher periods, you can select `m` as 6. +We recommend experimenting with `m` as it may depend on the specific problem. +Increase `m` in case the orbits are not being detected correctly. + +Initial conditions `ics` can be selected as a uniform grid of points in the state space or +subset of a chaotic trajectory. """ function davidchacklai(