Quartic Regression


The quartic regression option finds the equation of a fourth degree polynomial of the form

y = ax4 + bx3 + cx2 + dx + e


that best fits a set of data.

First, press selecting option AEDIT to enter the data .



The data shown here is the points {(2,11.4) (3,17) (5,27.3) (7,36.1) (11,47.7) (13,49.9)}



Press DREG to view the regression options.



For quadratic regression, select opton 06Rg_x4 using followed by five



Press and select quartic regression in the calculation screen. Now press followed by .



Therefore, the best-fit quartic equation for this data is approximately

y = .00011x4 - .0104x3 - .0504x2 + 6.037x - 3.89.


(Note the scientific notation for the first term.)

The regression equation can be automatically stored in the equation editor by entering the name of the equation, such as y1, after (L1,L2 as follows: choose option A and select y1 followed by .


Note: The resulting quartic equation is an exact fit if five non-collinear data points are entered.

The Sharp does not calculate the correlation coefficient r, but it does calculate the coefficient of determination, r2.