cubic regression with no quadratic term

C

Cyanlce

how do i do cubic regression without the quadratic term? how do i tell excel
there is no x^2? i just want it to be ax^3+bx+c
 
G

Guest

Cyanlce said:
how do i do cubic regression without the quadratic term? how do i tell excel
there is no x^2? i just want it to be ax^3+bx+c
Click to expand...


I presume you have a column of X and a column of Y data. Add a third
column which is your scoring function that you want to minimize.
Conventionally that would be something like { } = (Y - YourF(x))^2 At
the bottom of that column you sum up all your error function values.

Then you just use Solver to optimize the a, b, c values that you've used
in your scoring function equation to minimize the sum of your error
function values.

Good luck...

Bill
 
J

Jerry W. Lewis

Assuming that yData and xData are columnar data with no empty or
non-numeric cells, then select 3 contiguous cells in a row and array
enter (Ctrl-Shift-Enter)

=LINEST(yData,xData^{1,3})

As documented by Help, the reculting coeffients will be

(cubic, linear, intercept)

which is the opposite order to what you might expect.

Jerry
 
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