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Pig, mail # user - creating a graph over time


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Re: creating a graph over time
Guy Bayes 2011-10-28, 15:02
if it fits in R, it's trivial, draw a density plot or a histogram, about
three lines of R code

why I was wondering about the data volume.

His example is students attending classes, if  that is really the data hard
to believe it's super huge?

Guy

On Fri, Oct 28, 2011 at 6:12 AM, Norbert Burger <[EMAIL PROTECTED]>wrote:

> Perhaps another way to approach this problem is to visualize it
> geometrically.  You have a long series of class session instances, where
> each class session is like 1D line segment, beginning/stopping at some
> start/end time.
>
> These segments naturally overlap, and I think the question you're asking is
> equivalent to finding the number of overlaps at every subsegment.
>
> To answer this, you want to first break every class session into a full
> list
> of subsegments, where a subsegment is created by "breaking" each class
> session/segment into multiple parts at the start/end point of any other
> class session.  You can create this full set of subsegments in one pass by
> comparing pairwise (CROSS) each start/end point with your original list of
> class sessions.
>
> Once you have the full list of "broken" segments, then a final GROUP
> BY/COUNT(*) will you give you the number of overlaps.  Seems like approach
> would be faster than the previous approach if your class sessions are very
> long, or there are many overlaps.
>
> Norbert
>
> On Thu, Oct 27, 2011 at 4:05 PM, Guy Bayes <[EMAIL PROTECTED]> wrote:
>
> > how big is your dataset?
> >
> > On Thu, Oct 27, 2011 at 9:23 AM, Marco Cadetg <[EMAIL PROTECTED]> wrote:
> >
> > > Thanks Bill and Norbert that seems like what I was looking for. I'm a
> bit
> > > worried about
> > > how much data/io this could create. But I'll see ;)
> > >
> > > Cheers
> > > -Marco
> > >
> > > On Thu, Oct 27, 2011 at 6:03 PM, Norbert Burger <
> > [EMAIL PROTECTED]
> > > >wrote:
> > >
> > > > In case what you're looking for is an analysis over the full learning
> > > > duration, and not just the start interval, then one further insight
> is
> > > > that each original record can be transformed into a sequence of
> > > > records, where the size of the sequence corresponds to the session
> > > > duration.  In other words, you can use a UDF to "explode" the
> original
> > > > record:
> > > >
> > > > 1,marco,1319708213,500,math
> > > >
> > > > into:
> > > >
> > > > 1,marco,1319708190,500,math
> > > > 1,marco,1319708220,500,math
> > > > 1,marco,1319708250,500,math
> > > > 1,marco,1319708280,500,math
> > > > 1,marco,1319708310,500,math
> > > > 1,marco,1319708340,500,math
> > > > 1,marco,1319708370,500,math
> > > > 1,marco,1319708400,500,math
> > > > 1,marco,1319708430,500,math
> > > > 1,marco,1319708460,500,math
> > > > 1,marco,1319708490,500,math
> > > > 1,marco,1319708520,500,math
> > > > 1,marco,1319708550,500,math
> > > > 1,marco,1319708580,500,math
> > > > 1,marco,1319708610,500,math
> > > > 1,marco,1319708640,500,math
> > > > 1,marco,1319708670,500,math
> > > > 1,marco,1319708700,500,math
> > > >
> > > > and then use Bill's suggestion to group by course, interval.
> > > >
> > > > Norbert
> > > >
> > > > On Thu, Oct 27, 2011 at 11:05 AM, Bill Graham <[EMAIL PROTECTED]>
> > > > wrote:
> > > > > You can pass your time to a udf that rounds it down to the nearest
> 30
> > > > second
> > > > > interval and then group by course, interval to get counts for each
> > > > course,
> > > > > interval.
> > > > >
> > > > > On Thursday, October 27, 2011, Marco Cadetg <[EMAIL PROTECTED]>
> > wrote:
> > > > >> I have a problem where I don't know how or if pig is even suitable
> > to
> > > > > solve
> > > > >> it.
> > > > >>
> > > > >> I have a schema like this:
> > > > >>
> > > > >> student-id,student-name,start-time,duration,course
> > > > >> 1,marco,1319708213,500,math
> > > > >> 2,ralf,1319708111,112,english
> > > > >> 3,greg,1319708321,333,french
> > > > >> 4,diva,1319708444,80,english
> > > > >> 5,susanne,1319708123,2000,math
> > > > >> 1,marco,1319708564,500,french
> >