05-30-2015, 12:09 PM
I was messing around with some curve fitting on my 89 Titanium, since, while it would probably score dead last if we ranked calculators by usability * documentation quality / feature set, it's got a pretty decent stat package on board. (And it's actually not too shabby for programming, if you don't mind the horrible keyboard layout.)
If you run a linear regression, you get a value for corr. Nothing weird there. If you run a polynomial regression, you get R^2. But if you run one of the intrinsically linear regressions - LnReg, ExpEeg, and PowerReg, you get nothing indicating the quality of the fit.
Is there a mathematical reason for that, or is it just some really specific manifestation of laziness? My TI-86 and HP 48 both give correlation for those regression types, but nothing for polynomial (and the 48 just doesn't do polynomial period). The TI-36X Pro gives r and r^2 for the main four models, and R^2 for polynomial. My Casio fx-9860g Slim behaves similarly to the 36X Pro, and also reports MSe for a number of the models, which I'm not familiar with.
If you run a linear regression, you get a value for corr. Nothing weird there. If you run a polynomial regression, you get R^2. But if you run one of the intrinsically linear regressions - LnReg, ExpEeg, and PowerReg, you get nothing indicating the quality of the fit.
Is there a mathematical reason for that, or is it just some really specific manifestation of laziness? My TI-86 and HP 48 both give correlation for those regression types, but nothing for polynomial (and the 48 just doesn't do polynomial period). The TI-36X Pro gives r and r^2 for the main four models, and R^2 for polynomial. My Casio fx-9860g Slim behaves similarly to the 36X Pro, and also reports MSe for a number of the models, which I'm not familiar with.