# What is a conditional random field?

I new in machine learning, especially in Conditional Random Fields (CRF).

I have read several articles and papers and in there is always associated with HMM and sequences classification. I don't really understand mathematics, especially in the annoying formula. So I can't understand the process. Where I need to start to understand CRFs??

I want to make an information extraction application using CRF Named Entity Recognition (NER).

I got some tutorial for that: https://eli5.readthedocs.io/en/latest/tutorials/sklearn_crfsuite.html#training-data

But I don't know the proses each step, like training proses, evaluation, and testing

I use this code :

  data_frame = eli5.format_as_dataframes(
eli5.explain_weights_sklearn_crfsuite(self.crf))


Targets

Transition Features

How to get that number ?

and 1 more thing makes me confused:

crf = sklearn_crfsuite.CRF(
algorithm='lbfgs',
c1=0.1,
c2=0.1,
max_iterations=20,
all_possible_transitions=False,
)


What is the algorithm lbfgs? Is the CRF not an algorithm? Why do I need lbfgs? What is exactly a conditional random field?

• I will provide an answer later, but you will have to wait (unless someone provides an answer meanwhile). Anyway, it is ok to be confused when it comes to CRFs, especially if you don't have a solid mathematical background. – nbro Jul 14 '19 at 11:17
• okay, thank you for responding I really appreciate that @nbro – Faris Dewantoro Jul 14 '19 at 13:14
• heyy i still waiting your answer @nbro :( – Faris Dewantoro Jul 20 '19 at 10:28
• Hey! Sorry for having made you wait for a long time without warning you. CRFs involve a lot of concepts. So, a satisfactory will possibly be quite long, which would have required some time. Meanwhile, I couldn't have spent so much time to give this answer. I will try to give you an answer this weekend. – nbro Jul 20 '19 at 10:42
• @nbro Ok, i will waiting your answer :( – Faris Dewantoro Jul 20 '19 at 11:15