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thornahawk
μολών λαβέ
Active Member
Joined: 27 Mar 2005
Posts: 569
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 Posted: 10 Apr 2008 12:16:28 am Post subject: |
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Without using any of the LinReg commands, write the smallest possible linear regression routine that, given the x-coordinates stored in L1 and the y-coordinates stored in L2, will output the slope and y-intercept of the best-fit line of a given set of points.
You can of course check the validity of your routine by comparing results with any of the two LinReg functions. ;)
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emperorwiggy
Newbie
Joined: 27 Mar 2008
Posts: 27
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| Posted: 10 Apr 2008 07:12:36 am Post subject: |
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Is there any particular reason why you can't use the LinReg command? Besides making it really hard? :biggrin:
I could do it with a numstring subroutine that doesn't use linreg, but I don't have one. |
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DarkerLine
ceci n'est pas une |
Super Elite (Last Title)
Joined: 04 Nov 2003
Posts: 8328
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| Posted: 10 Apr 2008 08:29:23 am Post subject: |
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This is probably cheating:
Quote: e^(L2→L2
ExpReg
ln({b,a
I suggest the rules be changed to not allow use of any regressions (including LinRegTTest, or on the newer calculators LinRegTInt)
Last edited by Guest on 10 Apr 2008 08:32:39 am; edited 1 time in total |
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thornahawk
μολών λαβέ
Active Member
Joined: 27 Mar 2005
Posts: 569
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| Posted: 10 Apr 2008 09:52:27 am Post subject: |
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"Besides making it really hard?"
- Well, the name of the forum has "Brain Teasers" in it, so... ;)
"This is probably cheating..."
- Yes it is. :P
"I suggest the rules be changed to not allow use of any regressions (including LinRegTTest, or on the newer calculators LinRegTInt)"
- Yes indeed. No built-in regression functions please, Louise. :P
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DarkerLine
ceci n'est pas une |
Super Elite (Last Title)
Joined: 04 Nov 2003
Posts: 8328
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| Posted: 10 Apr 2008 09:44:06 pm Post subject: |
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Okay, here's an honest attempt:
Quote: 2-Var Stats
Matr►list(rref([[Σx²,Σx,Σxy][Σx,n,Σy]]),3,L₃
The routine outputs the result in L₃ as the pair {slope, y-intercept}. If you want the result to be displayed as well, add L₃ as a final line.
Last edited by Guest on 02 Aug 2010 02:33:09 am; edited 1 time in total |
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thornahawk
μολών λαβέ
Active Member
Joined: 27 Mar 2005
Posts: 569
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| Posted: 11 Apr 2008 12:39:00 am Post subject: |
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Wow, that is short!  Here was my attempt:
Quote: mean(L₁→T
mean((L₁-Ans)L₂)/mean((L₁-Ans)²
{Ans,mean(L₂)-AnsT
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Weregoose
Authentic INTJ
Super Elite (Last Title)
Joined: 25 Nov 2004
Posts: 3976
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DarkerLine
ceci n'est pas une |
Super Elite (Last Title)
Joined: 04 Nov 2003
Posts: 8328
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| Posted: 11 Apr 2008 01:33:30 pm Post subject: |
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A minor optimization to the second line of your routine: (Σxy/n-XY)/σx²
Last edited by Guest on 02 Aug 2010 02:32:56 am; edited 1 time in total |
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