Function printE5

Example

// TypeScript usage example
import {printE5} from 'diff-grok';

printE5();
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# Python reference calculation for comparison
import numpy as np
import pandas as pd
from scipy.integrate import solve_ivp

# -------------------------
# 0. Solver method
# -------------------------
METHOD = "Radau"  # stiff solver recommended

# -------------------------
# 1. Define E5 constants
# -------------------------
K1 = 7.89e-10
K2 = 1.13e9
K3 = 1.1e7
K4 = 1.13e3

# -------------------------
# 2. Define E5 ODE
# -------------------------
def e5(t, y):
   y1, y2, y3, y4 = y
   dy = np.zeros(4)
   dy[0] = -K1 * y1 - K3 * y1 * y3
   dy[1] =  K1 * y1 - K2 * y2 * y3
   dy[2] =  K1 * y1 - K2 * y2 * y3 - K3 * y1 * y3 + K4 * y4
   dy[3] =  K3 * y1 * y3 - K4 * y4
   return dy

# -------------------------
# 3. Initial conditions and time
# -------------------------
y0 = [0.00176, 0, 0, 0]
t_start = 0.0
t_end = 1e6
t_step = 2.5e3

# Ensure t_eval is within t_span
n_points = int(np.ceil((t_end - t_start) / t_step)) + 1
t_eval = np.linspace(t_start, t_end, n_points)

# -------------------------
# 4. Solve ODE
# -------------------------
sol = solve_ivp(
   e5,
   (t_start, t_end),
   y0,
   method=METHOD,
   t_eval=t_eval,
   rtol=1e-6,
   atol=1e-6
)

print("Success:", sol.success)
print("Message:", sol.message)

# -------------------------
# 5. Save solution to CSV
# -------------------------
data = np.column_stack((sol.t, sol.y.T))
col_names = ['t', 'y1', 'y2', 'y3', 'y4']

df = pd.DataFrame(data, columns=col_names)
filename = f"E5-using-{METHOD}.csv"
df.to_csv(filename, index=False)

print(f"Solution saved to '{filename}'")
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