Function printRobertson

Example

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

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

METHOD = "Radau" # "BDF" or "LSODA"

# -------------------------
# 1. Define Robertson ODE
# -------------------------
def robertson(t, y):
   A, B, C = y
   dA = -0.04 * A + 1e4 * B * C
   dB = 0.04 * A - 1e4 * B * C - 3e7 * B**2
   dC = 3e7 * B**2
   return [dA, dB, dC]

# -------------------------
# 2. Initial conditions
# -------------------------
y0 = [1.0, 0.0, 0.0]
t_start = 0.0
t_end = 1e11
t_step = 2.5e6
t_span = (t_start, t_end)

# Output points
t_eval = np.arange(t_start, t_end + t_step, t_step)

# -------------------------
# 3. Solve ODE
# -------------------------
sol = solve_ivp(
   robertson,
   t_span,
   y0,
   method=METHOD,
   t_eval=t_eval,
   rtol=1e-7,
   atol=1e-7
)

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

# sol.t → time array, sol.y.T → concentrations (n_points, 3)
data = np.column_stack((sol.t, sol.y.T))

# Create DataFrame with headers
df = pd.DataFrame(data, columns=['time', 'A', 'B', 'C'])

# Save to CSV
df.to_csv(f'ROBER-using-{METHOD}.csv', index=False)
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