On Sunday, May 11, 2014 12:57:34 AM UTC+5:30, subhaba...@gmail.com wrote: > Dear Room, > > > > I was trying to go through a code given in > http://en.wikipedia.org/wiki/Forward%E2%80%93backward_algorithm[ Forward > Backward is an algorithm of Machine Learning-I am not talking on that > > I am just trying to figure out a query on its Python coding.] > > > > I came across the following codes. > > > > >>> states = ('Healthy', 'Fever') > > >>> end_state = 'E' > > >>> observations = ('normal', 'cold', 'dizzy') > > >>> start_probability = {'Healthy': 0.6, 'Fever': 0.4} > > >>> transition_probability = { > > 'Healthy' : {'Healthy': 0.69, 'Fever': 0.3, 'E': 0.01}, > > 'Fever' : {'Healthy': 0.4, 'Fever': 0.59, 'E': 0.01}, > > } > > >>> emission_probability = { > > 'Healthy' : {'normal': 0.5, 'cold': 0.4, 'dizzy': 0.1}, > > 'Fever' : {'normal': 0.1, 'cold': 0.3, 'dizzy': 0.6}, > > } > > > > def fwd_bkw(x, states, a_0, a, e, end_st): > > L = len(x) > > fwd = [] > > f_prev = {} #THE PROBLEM > > # forward part of the algorithm > > for i, x_i in enumerate(x): > > f_curr = {} > > for st in states: > > if i == 0: > > # base case for the forward part > > prev_f_sum = a_0[st] > > else: > > prev_f_sum = sum(f_prev[k]*a[k][st] for k in states) ## > > > > f_curr[st] = e[st][x_i] * prev_f_sum > > > > fwd.append(f_curr) > > f_prev = f_curr > > > > p_fwd = sum(f_curr[k]*a[k][end_st] for k in states) > > > > As this value was being called in prev_f_sum = sum(f_prev[k]*a[k][st] for k > in states marked ## > > I wanted to know what values it is generating. > > So, I had made the following experiment, after > > for i, x_i in enumerate(x): > > I had put print f_prev > > but I am not getting how f_prev is getting the values. > > > > Here, > > x=observations, > > states= states, > > a_0=start_probability, > > a= transition_probability, > > e=emission_probability, > > end_st= end_state > > > > Am I missing any minor aspect? > > Code is running fine. > > > > If any one of the esteemed members may kindly guide me. > > > > Regards, > > Subhabrata Banerjee.
Dear Sir, Thank you for your kind reply. I will check. Regards, Subhabrata Banerjee. -- https://mail.python.org/mailman/listinfo/python-list
