import pandas as pd
from IOHMM import UnSupervisedIOHMM, OLS, CrossEntropyMNL

# Create a single length sequence
df_single = pd.DataFrame({
    'rt': [5.0],  # response
    'feature': [1.0]  # covariate
})
  
# Set up IOHMM model
model = UnSupervisedIOHMM(num_states=1, max_EM_iter=10, EM_tol=1e-4)
model.set_models(
    model_initial=CrossEntropyMNL(solver='lbfgs'),
    model_transition=CrossEntropyMNL(solver='lbfgs'),
    model_emissions=[OLS()]
)
model.set_inputs(
    covariates_initial=[],
    covariates_transition=['feature'],
    covariates_emissions=[['feature']]
)
model.set_outputs([['rt']])

# Set data and train
model.set_data([df_single])
model.train()

  File "/root/IOHMM/test.py", line 26, in <module>
    model.train()
  File "/root/IOHMM/IOHMM/IOHMM.py", line 403, in train
    self.M_step()
  File "/root/IOHMM/IOHMM/IOHMM.py", line 383, in M_step
    self.model_transition[st].fit(X, Y)
  File "/root/IOHMM/IOHMM/linear_models.py", line 905, in fit
    X, sample_weight = self._transform_X_sample_weight(X, sample_weight=sample_weight)
  File "/root/IOHMM/IOHMM/linear_models.py", line 180, in _transform_X_sample_weight
    X = self._transform_X(X)
  File "/root/IOHMM/IOHMM/linear_models.py", line 149, in _transform_X
    X = add_constant(X, has_constant='add')
  File "/root/IOHMM/.venv/lib/python3.10/site-packages/statsmodels/tools/tools.py", line 195, in add_constant
    is_nonzero_const = np.ptp(x, axis=0) == 0
  File "/root/IOHMM/.venv/lib/python3.10/site-packages/numpy/core/fromnumeric.py", line 2684, in ptp
    return _methods._ptp(a, axis=axis, out=out, **kwargs)
  File "/root/IOHMM/.venv/lib/python3.10/site-packages/numpy/core/_methods.py", line 220, in _ptp
    umr_maximum(a, axis, None, out, keepdims),
ValueError: zero-size array to reduction operation maximum which has no identity