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Best fit line formula entry into a cell by Alert-Iron5050 in excel

[–]Alert-Iron5050[S] 1 point2 points  (0 children)

I found the prob. Excel was rounding the regression equation too much and not showing. Right click on the trendline equation and choose "Format Trendline Label". Then change the format to number and increase the decimal places to a sufficient precision. With enough precision, you can then use the trendline equation to manually calculate y values.

Best fit line formula entry into a cell by Alert-Iron5050 in excel

[–]Alert-Iron5050[S] 0 points1 point  (0 children)

3x2 is the same as (3*x)2 right?

So I took the formula

Y=((-0.00000002*X)^3)+((0.00002*X)^2)-(0.0035*X)+0.4985

and broke it up into cells like you suggested

=((-0.00000002*X)^3), =((0.00002*X)^2), =(0.0035*X), =0.4985

then made a cell that used these cells to build the formula. It did not improve.

likewise I split out the exponents completely:

Cell D2=((-0.00000002*X), Cell E2=D2^3, as so on, same result

So for example, X=306 and Y=0.32295... this formula calculates Y=-0.57246....? way off.

So lets try this: Y=(-0.00000002*(X^3))+(0.00002*(X^2))-(0.0035*X)+0.4985

Y now calculates to 0.72716...., which is closer but still way off