Finding Mean - Intro to Hadoop and MapReduce

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So let's do it. Let's calculate mean
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and standard deviation. And to do that, let's
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think back to our example with stores and
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sales. And let's say the question we want to
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answer is, is there any correlation between the
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day of the week and how much money
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people spend on various items? And what's interesting
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mapper has to do is, I'll put the day of the week as a key, so maybe Monday, and
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the value of a sale, maybe \$5.20 as a value.
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That's it. What does that leave for the reducer? Well,
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it leaves all the math for the reducer. And the
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general reason for this rule of thumb, for what the
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mapper and reducer are doing, comes from the fact that
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oftentimes with these, with these summary statistics, you sort of need
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to know all of the statistics or all of
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the parent data before you can make any calculations. So
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we don't want to jump the gun and have the mapper
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do calculations before it's ready. So why don't you go
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ahead and calculate the mean and standard deviation for
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sales for each day of the week, to help us
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try to answer this question. If there's any correlation between
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the day of the week and how much people spend.
Tytuł:
Finding Mean - Intro to Hadoop and MapReduce
Opis:

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Video Language:
English
Team:
Udacity
Projekt:
ud617 - Intro to Hadoop and Mapreduce
Duration:
01:15
 Udacity Robot edited angielski subtitles for 07-09 Finding Mean Udacity Robot edited angielski subtitles for 07-09 Finding Mean Cogi-Admin edited angielski subtitles for 07-09 Finding Mean

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