experiences with big data by srinivasan seshadri
TRANSCRIPT
EXPERIENCES WITH BIG DATASRINIVASAN SESHADRI, FOUNDER ZETTATA
WORLD BEFORE BIG DATA
It is a Capital Mistake to Theorize before one has Data Sherlock Holmes
HOWEVER, DO NOT WANT TO BE HERE
AXIOMS
• Measure, Measure, Measure
• Garbage in, Garbage out
• Correlation is not Causation
• More Data Beats Cleverer Algorithms
• Algorithms that do better with more data are more interesting
• Independent Sources Of data add new signals
• Feature Engineering is the key to being a good data scientist
• How do machines and Human interplay in Big Data?
• Learn many models ‐ ensembles
• Outliers are always interesting..
MEASURE, MEASURE, MEASURE
• Have a Hypothesis• Create a metric to determine if hypothesis is correct• Build a solution that can be measured • Iterate
If you can not measure it you can not improve it – Lord Kelvin
GARBAGE IN GARBAGE OUT
WHAT DO YOU WANT THE ANSWER TO BE?
CORRELATIONS
CORRELATION IS NOT CAUSATION
• Correlation in Data Need Not Imply Correlation in Real Life
• Can find random correlations in large amounts of data
• Correlation Does Not Imply Causation
CORRELATION IS NOT CAUSATION
CORRELATION STRIKES AGAIN!!
MORE DATA BEATS CLEVERER ALGORITHMS
• Adding IMDB data For Netflix prize
• Adding Protein Expression Data or Patient Data to Gene Expression Data
• Bag of Words Approach for Word Sense Disambiguation
WORD SENSE DISAMBIGUATION
• Bank
• Sloping Land Alongside a river or a lake. It typically has thick vegetation growing..
• A financial institution that takes deposits from some customers and gives loans to others who require the money.
To disambiguate in typical sentences look for co‐occurrences of words with words in definition. Unsupervised Learning. Bootstrap a model.
The pilot landed the plane on the Hudson River amongst several boats and an appreciative audience cheered from the banks of the river.
He issued a check and took it to the bank so he could transfer money.
Can look for frequent co‐occurrences with each sense of the word (boats and check respectively) and build a larger bag of words in which to disambiguate.
WORD SENSE DISAMBIGUATION
FEATURE ENGINEERING
Can not expect arbitrarily complex models to be learned by the computer
FEATURE ENGINEERING
CITYY 1 LAT. CITY 1 LNG. CITY 2 LAT. CITY 2 LNG. DRIVABLE?
123.24 46.71 121.33 47.34 Yes
123.24 56.91 121.33 55.23 Yes
123.24 46.71 121.33 55.34 No
123.24 46.71 130.99 47.34 No
FEATURE ENGINEERING
DISTANCE (MI.) DRIVABLE?
14 Yes
28 Yes
705 No
2432 No
OF HUMANS AND MACHINES• Partnership is important
• Aha moment and the strategy comes from humans..
• Machines do the hard work of calculating fast and do not tire
• Maybe some day Machines will be able to do more than they are asked to do explicitly.. Today Explicit Instructions are the norm..
ENSEMBLES ‐ OUTLIERS ARE NOT INTERESTING – FOR CLASSIFIERS
• Learn many models from random subsets of training data
• Effect of outliers is reduced on a majority of the models
• Random Forests
OUTLIERS ARE ALWAYS INTERESTING FOR RANKING PROBLEMS
• You have to be so good that they can not ignore you• My personal thesis: Average in everything is boring. Be outstanding in something.
• Outliers along some dimension always have interesting information – whenever you are combining multiple variables to come up with one global rank• Search• Job Interviews!
UNKNOWN UNKNOWNS – VERY INTERESTING TO A BUSINESS – OUTLIERS
BIG DATA AND HEALTHCARE
ARE YOU IN THE JOB MARKET?