Statistics 2Var Power curve fit

05102017, 09:32 PM
Post: #1




Statistics 2Var Power curve fit
I was playing with the curve fitting function/plotting and while trying the Power curve fit (bx^m) with the following data:
0 0 1 1 2 1.4 3 1.7 4 2 9 3 16 4 25 5 36 6 which should fit b=1, m= 0.5 pretty easily, I keep getting a "S1  Error Insufficient statistics data" The others work fine  though I cannot guarantee I have tried all of them... What is wrong? 

05102017, 10:14 PM
Post: #2




RE: Statistics 2Var Power curve fit
Suggestion: Try deleting the (0,0) data point. Most curvefit software balks at negative and zero data for power fits, since it needs to take the log of the data.
<0ɸ0> Joe 

05102017, 10:37 PM
Post: #3




RE: Statistics 2Var Power curve fit
Thanks.
I believe that was it. I reset the app and tried it again and it worked! I was about to chalk it up to a weird state issue, but added a 0,0 point and it fails. I think the error can be a little more clear. I was thinking it was a "number of points based on the order of the polynomial" issue, so I kept adding points and no joy. Hard to believe that that error could be solved by *removing* points! 

05132017, 02:55 AM
Post: #4




RE: Statistics 2Var Power curve fit
(05102017 10:37 PM)KeithB Wrote: I think the error can be a little more clear. Agreed. The HP 50g (with the same stats data as above, and set to the PWRFIT model) reports "LR Error: Invalid Σ Data LN(0)", which is a more helpful error message than Prime's. <0ɸ0> Joe 

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