May 04, 2016

# (more) Fun with Markov Chains

Expanded & improved version of this talk given at the Memphis Machine Learning & Data Science meetup. http://www.meetup.com/memphis-technology-user-groups/events/230024221/

May 04, 2016

## Transcript

2. ### what is a markov chain? A stochastic process… sequence of

random variables… serial dependence only between adjacent periods… …systems that follow a chain of linked events, where what happens next depends only on the current state of the system.

5. ### markov models & text A Mathematical Theory of Communication 1949

paper by Claude Shannon
6. ### Example from Wikipedia: A creature who eats only grapes, cheese,

or lettuce, based on these rules: • It eats once a day. • If it ate cheese today, tomorrow it will eat lettuce or grapes with equal probability. • If it ate grapes today, tomorrow it will eat • grapes with probability 1/10 • cheese with probability 4/10 • lettuce with probability 5/10. • If it ate lettuce today, tomorrow it will eat • grapes with probability 4/10 • cheese with probability 6/10 • It will not eat lettuce again tomorrow.

8. ### – King James Programming http://kingjamesprogramming.tumblr.com/ “17:20 O LORD, there is

none end of the regexp.”
9. ### – Erowid Recruiter https://twitter.com/erowidrecruiter “Good morning, I saw your profile

looks like a very long profile and thought it looked like monsters and I am an executive recruiter”

net.singles
12. ### How does it work? 1. Train it on a bunch

of text. 2. Let it generate some text. 3. Commence Hijinks
13. ### – Edgar Allen Frost “But tis not true that thus

I dwelt aloof For the rare and radiant maiden whom the angels name Lenore.”
14. ### A Patch of Old Snow There's a patch of old

snow in a corner That I should have guessed Was a blow-away paper the rain Had brought to rest. It is speckled with grime as if Small print overspread it, The news of a day I've forgotten-- If I ever read it.
15. ### A Patch of Old Snow There's a patch of old

snow in a corner That I should have guessed Was a blow-away paper the rain Had brought to rest. It is speckled with grime as if Small print overspread it, The news of a day I've forgotten-- If I ever read it.
16. ### A Patch of Old Snow There's a patch of old

snow in a corner That I should have guessed Was a blow-away paper the rain Had brought to rest. It is speckled with grime as if Small print overspread it, The news of a day I've forgotten-- If I ever read it.
17. ### A Patch of Old Snow There's a patch of old

snow in a corner That I should have guessed Was a blow-away paper the rain Had brought to rest. It is speckled with grime as if Small print overspread it, The news of a day I've forgotten-- If I ever read it.
18. ### A Patch of Old Snow There's a patch of old

snow in a corner That I should have guessed Was a blow-away paper the rain Had brought to rest. It is speckled with grime as if Small print overspread it, The news of a day I've forgotten-- If I ever read it.
19. ### { (‘And', 'the'): ['sweet', 'pear', 'cloud', 'stars', 'silken', 'only', 'Raven',

‘lamplight’], } A word pair. Words that always follow the pair
20. ### A Patch of Old Snow There's a patch of old

snow in a corner That I should have guessed Was a blow-away paper the rain Had brought to rest. It is speckled with grime as if Small print overspread it, The news of a day I've forgotten-- If I ever read it.
21. ### [ ('my', 'loss.'), ('all', 'windstirred.'), ('to', 'rest.'), ('read', 'it.'), ('time',

'talk.'), ('friendly', 'visit.'), ('in', 'ice.'), ('favour', 'fire.'), ('would', ‘suffice.'), … ] A list of all line endings.

23. ### 1. Pick a random ending pair. 2. Use that as

a key to pick a random word { (‘still', ‘abide.’): [‘But'] }
24. ### 1. Pick a random ending pair. 2. Use that as

a key to pick a random word { (‘still', ‘abide.’): [‘But'] } Output: But key: (‘abide.’, ‘But’) 3. Keep the word; use it as part of your key.
25. ### Output: But lookup: {(‘abide', ‘But’): [‘tis']} 4. Keep doing this…

Output: But tis lookup: {(‘But', ‘tis’): [‘not']} Output: But tis not lookup: {(‘tis', ‘not’): [‘true']} Output: But tis not true that lookup: {(‘not', ‘true’): [‘that']}
26. ### Output: But tis not true that thus lookup: {(‘that', ‘thus’):

[‘I']} Output: But tis not true that thus I lookup: {(‘thus', ‘I’): [‘dwelt']} Output: But tis not true that thus I dwelt lookup: {(‘I', ‘dwelt’): [‘aloof']} Output: But tis not true that thus I dwelt aloof lookup: {(‘dwelt', ‘aloof’): [‘For']}
27. ### Key:(‘read', ‘it.’) 5. Until your key is a sentence ending.

But tis not true that thus I dwelt aloof For the rare and radiant maiden whom the angels in Heaven above Nor the demons down under the sea In her sepulchre there by the sea A wind blew out of a day I've forgotten If I ever read it.