147 reputation
5
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location Bay Area, CA
age
visits member for 2 years, 10 months
seen Dec 14 at 11:26

Web application developer at Google.

Prior open source work:
www.gpxcreator.com

Click here to learn about recursion!


Sep
24
awarded  Autobiographer
Mar
11
comment Number of different ways to join 4 tables
Wow. Good info, albeit maybe deeper than my brain can go at the moment. Thanks for the links though, I will try to digest them. I'm not sure I entirely understand the formula in your conclusion... what does that give you for N = 4? Maybe I will take your advice and see if I can get this migrated to Math.
Mar
10
comment Number of different ways to join 4 tables
@usr I'm not sure what you mean by join definition, other than the obvious: a binary operation between 2 tables that selects a subset of a cross product satisfying some predicate. The text I pasted is from a chapter on dynamic programming cost-based query optimization, and if it helps, the sentence that proceeds it reads "For the sake of simplicity when discussing dynamic programming, let’s consider the case of joining N relations together in an N-way join, that is, “R1 JN R2 . . . JN RN−1 JN RN.”
Mar
10
asked Number of different ways to join 4 tables
Mar
1
awarded  Editor
Mar
1
accepted How to correct/filter inaccurate speeds calculated from a GPS track
Mar
1
comment How to correct/filter inaccurate speeds calculated from a GPS track
Yeah, that's what I'm doing for now. Some day I'll try to learn about Kalman filters and it will be interesting to compare the results, but for now I'll probably leave it like this. Thanks. I'll accept your answer unless a better one gets posted. :-P
Mar
1
revised How to correct/filter inaccurate speeds calculated from a GPS track
added 4 characters in body
Mar
1
comment How to correct/filter inaccurate speeds calculated from a GPS track
@bubba yes that was a typo, thanks. ;-)
Mar
1
comment How to correct/filter inaccurate speeds calculated from a GPS track
@VincentTjeng thanks for the link. I'd actually already come up with using a moving average on my own (5 points seems to work pretty well), but I figured I'd see what else was out there. Looks like if I'm serious I'll have to dig deep and learn about the Kalman filters. Thanks.
Mar
1
asked How to correct/filter inaccurate speeds calculated from a GPS track
Feb
12
comment Confusion from a textbook comment about induction
Thanks for the quick responses all. It is much more clear now.
Feb
12
accepted Confusion from a textbook comment about induction
Feb
12
asked Confusion from a textbook comment about induction
Feb
2
awarded  Supporter
Feb
2
awarded  Scholar
Feb
2
accepted Strange set notation (a set as a power of 2)?
Feb
1
awarded  Student
Feb
1
asked Strange set notation (a set as a power of 2)?