miscellaneous helper functions for estimating IRT models
estimate_nr_iteration updates the parameters using the newton-raphson method
estimate_nr_iteration(param, free, dv, h_max, lr, bound)model_polytomous_3dindex(u)
model_polytomous_3dresponse(u)
the parameter being estimated
TRUE to freely estimate specific parameters
the first and second derivatives
the maximum value of h
the learning rate
the lower and upper bounds of the parameter
the observed response, 2d matrix, values start from 0