From d21625a3cd9677c4d2ee817298e7625e99667c9c Mon Sep 17 00:00:00 2001
From: sotech117 <michael_foiani@brown.edu>
Date: Wed, 21 Feb 2024 12:19:28 -0500
Subject: finish first 3 problems - codewise

---
 hw3/Lorenz.jl | 59 +++++++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 47 insertions(+), 12 deletions(-)

(limited to 'hw3/Lorenz.jl')

diff --git a/hw3/Lorenz.jl b/hw3/Lorenz.jl
index 0144c92..c4c501d 100644
--- a/hw3/Lorenz.jl
+++ b/hw3/Lorenz.jl
@@ -1,8 +1,13 @@
 using DifferentialEquations
 using Plots
 
-# Simulate Lorenz 63 system and investigate sensitivity to initial conditions
+r_max = 160
+r_steps = 320
+
+sim_time = 1000.0
 
+# STEP 1, go over each value of r and store the results
+# Simulate Lorenz 63 system and investigate sensitivity to initial conditions
 function tendency!(du, u, p, t)
     x,y,z = u
     σ,ρ,β = p
@@ -12,21 +17,51 @@ function tendency!(du, u, p, t)
     du[3] = dz = x*y - β*z
 end
 
-p = [10.0, 28.0, 8/3] # parameters of the Lorentz 63 system
-tspan = (0.0, 1000.0)
 
-u0 = [1.0, 0.0, 0.0]
-δu0 = [0.0, 0.001, 0.0] # small deviation in initial condition
+# make a linspace for these values of r
+r_values = range(0, r_max, length=r_steps)
+sols = []
+for i in 1:r_steps
+    r = r_values[i]
+    p = [10.0, r, 8/3] # parameters of the Lorentz 63 system
+    tspan = (0.0, sim_time)
 
-prob = ODEProblem(tendency!, u0, tspan, p)
-sol1 = solve(prob, Tsit5(), reltol=1e-8, abstol=1e-8) # control simulation
+    u0 = [1.0, 0.0, 0.0]
+    prob = ODEProblem(tendency!, u0, tspan, p)
+    sol = solve(prob, Tsit5(), reltol=1e-8, abstol=1e-8) # control simulation
 
+    push!(sols, sol)
 
-prob = ODEProblem(tendency!, u0 + δu0, tspan, p)
-sol2 = solve(prob, Tsit5(), reltol=1e-8, abstol=1e-8) # perturbed initial condition
+    println("r=$r")
+end
+
+# STEP 2, map data to arrays where plane crosses the x-axis
+r_maxes = []
+z_maxes = []
+r_mins = []
+z_mins = []
+for i in 1:r_steps
+    println("i: ", length(sols[i].t))
+    z_values = sols[i][3, :]
+    # iterate over to find the local maxima and minima
+    # take off the first 300 values to avoid transient
+    for j in 301:length(z_values)-1
+        if z_values[j] > z_values[j-1] && z_values[j] > z_values[j+1]
+            push!(r_maxes, r_values[i])
+            push!(z_maxes, z_values[j])
+        end
+        if z_values[j] < z_values[j-1] && z_values[j] < z_values[j+1]
+            push!(r_mins, r_values[i])
+            push!(z_mins, z_values[j])
+        end
+    end
+end
 
-plot(sol1, idxs = (1, 2, 3)) # 3d plot
+# println("r_maxes: ", r_maxes)
+# println("z_maxes: ", z_maxes)
 
-# plot(sol1, idxs = (1, 2))
+# STEP 3, plot the bifurcation diagram
+plot(r_maxes, z_maxes, seriestype = :scatter, mc=:blue, ms=.25, ma=0.25, label="Maxima")
+plot!(r_mins, z_mins, seriestype = :scatter, mc=:green, ms=.25, ma=0.25, label="Minima")
 
-plot([sol1[1, :], sol2[1, :]], [sol1[2, :], sol2[2, :]])
\ No newline at end of file
+savefig("hw3/test3.png")
\ No newline at end of file
-- 
cgit v1.2.3-70-g09d2