def benchmark_lambda(train_df, train_df_lifted, modfile, solver):
fig, ax = plt.subplots(2, 2, figsize=(9, 7))
theta = {}
theta[0], _ = solve_and_subplot(
train_df, train_df_lifted, 0, ax[0, 0], modfile, solver
)
theta[0.1], _ = solve_and_subplot(
train_df, train_df_lifted, 0.1, ax[0, 1], modfile, solver
)
theta[1], _ = solve_and_subplot(
train_df, train_df_lifted, 1, ax[1, 0], modfile, solver
)
theta[10], _ = solve_and_subplot(
train_df, train_df_lifted, 10, ax[1, 1], modfile, solver
)
plt.show()
return theta