File:Hopf and homoclinic bifurcation 2.gif
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Summary
DescriptionHopf and homoclinic bifurcation 2.gif |
English: Matplotlib codefrom tqdm import tqdm
import numpy as np
import matplotlib.pyplot as plt
from scipy.integrate import solve_ivp
import os
escape_size = 2.0 # If a trajectory is this distance away from 0, we assume it has escaped and stop simulating it.
for i, mu in enumerate(tqdm(np.linspace(-0.18, 0.15, 240))):
if i < 129:
continue
def system(t, y):
v, w = y
dv = mu * v + w - v**2
dw = -v + mu * w + 2 * v**2
dv *= (np.abs(v) < 2.0) * (np.abs(w) < 2.0)
dw *= (np.abs(v) < 2.0) * (np.abs(w) < 2.0)
return [dv, dw]
def system_reversed(t, y):
v, w = y
dv = mu * v + w - v**2
dw = -v + mu * w + 2 * v**2
dv *= (np.abs(v) < 2.0) * (np.abs(w) < 2.0)
dw *= (np.abs(v) < 2.0) * (np.abs(w) < 2.0)
return [-dv, -dw]
x_root = (mu**2+1)/(2+mu)
y_root = -mu * x_root + x_root ** 2
vmin, vmax, wmin, wmax = -1,1,-1,1
# vmin,vmax,wmin,wmax= x_root-0.0005,x_root+0.0005, y_root-0.0005, y_root+0.0005
t_span = np.array([0, 20])
trajectory_resolution = 10
epsilon = 0.01
initial_conditions = [(x, y) for x in np.linspace(vmin, vmax, trajectory_resolution) for y in np.linspace(wmin, wmax, trajectory_resolution)]
initial_conditions += [(0 + dx, 0 + dy) for dx in np.linspace(-0.02, 0.02, 3) for dy in np.linspace(-0.02, 0.02, 3)]
initial_conditions_2 = [(x_root + dx, y_root + dy) for dx in np.linspace(-epsilon, epsilon, 10) for dy in np.linspace(-epsilon, epsilon, 10)]
sols = {}
sols_2 = {}
sols_reversed = {}
sols_reversed_2 = {}
for ic in initial_conditions:
sols[ic] = solve_ivp(system, t_span, ic, dense_output=True, max_step=0.05)
sols_reversed[ic] = solve_ivp(system_reversed, t_span, ic, dense_output=True, max_step=0.05)
for ic in initial_conditions_2:
sols_2[ic] = solve_ivp(system, 2*t_span, ic, dense_output=True, max_step=0.05)
sols_reversed_2[ic] = solve_ivp(system_reversed, 2*t_span, ic, dense_output=True, max_step=0.05)
vs = np.linspace(vmin, vmax, 200)
v_axis = np.linspace(vmin, vmax, 20)
w_axis = np.linspace(wmin, wmax, 20)
v_values, w_values = np.meshgrid(v_axis, w_axis)
dv, dw = system(0, [v_values, w_values])
fig, ax = plt.subplots(figsize=(16,16))
# ax.scatter(x_root, y_root)
# integral curves
for ic in initial_conditions:
sol = sols[ic]
ax.plot(sol.y[0], sol.y[1],alpha=0.4, linewidth=0.5, color='k')
sol = sols_reversed[ic]
ax.plot(sol.y[0], sol.y[1], alpha=0.4, linewidth=0.5, color='k')
for ic in initial_conditions_2:
sol = sols_2[ic]
ax.plot(sol.y[0], sol.y[1],alpha=0.8, linewidth=0.5, color='r')
sol = sols_reversed_2[ic]
ax.plot(sol.y[0], sol.y[1], alpha=0.8, linewidth=0.5, color='b')
# vector fields
arrow_lengths = np.sqrt(dv**2 + dw**2)
alpha_values = 1 - (arrow_lengths / np.max(arrow_lengths))**0.4
ax.quiver(v_values, w_values, dv, dw, color='blue', linewidth=0.5, scale=25, alpha=alpha_values)
# nullclines
ax.plot(vs, vs**2-mu*vs, color="green", alpha=0.2, label="x nullcline")
if np.abs(mu) < 0.001:
ax.axvline(0, wmin, wmax, color="red", alpha=0.2, label="y nullcline")
ax.axvline(1/2, wmin, wmax, color="red", alpha=0.2, label="y nullcline")
else:
ax.plot(vs, (vs-2*vs**2)/mu, color="red", alpha=0.2, label="y nullcline")
ax.set_title(f'Hopf Bifurcation Model
$\mu={mu:.3f}}})
# ax.legend()
ax.set_xlim(vmin, vmax)
ax.set_ylim(wmin, wmax)
ax.set_xticks([])
ax.set_yticks([])
dir_path = f"./hopf_2"
if not os.path.exists(dir_path):
os.makedirs(dir_path)
fig.savefig(f"{dir_path}/{i}.png")
plt.close()
import imageio.v3 as iio
from natsort import natsorted
import moviepy.editor as mp
for dir_path in ["./hopf_2"]:
file_names = natsorted((fn for fn in os.listdir(dir_path) if fn.endswith('.png')))
# Create a list of image files and set the frame rate
images = []
fps = 24
# Iterate over the file names and append the images to the list
for file_name in file_names:
file_path = os.path.join(dir_path, file_name)
images.append(iio.imread(file_path))
filename = dir_path[2:]
iio.imwrite(f"{filename}.gif", images, duration=1000/fps, rewind=True)
clip = mp.ImageSequenceClip(images, fps=fps)
clip.write_videofile(f"{filename}.mp4")
|
Date | |
Source | Own work |
Author | Cosmia Nebula |
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 19:08, 26 April 2023 | ![]() | 1,600 × 1,600 (53.45 MB) | Cosmia Nebula | Uploaded while editing "Bifurcation theory" on en.wikipedia.org |
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