Area under a curve in Excel.

[kokonut]

Hello all,
Is it possible to find the area under a curve (or trendline, more importantly) in Microsoft Excel?
I have some curves in Excel and have fitted trendlines to these curves based on sixth order polynomials. I need to know if there is an add-in or function that will save me the trouble of integrating the polynomials myself.
Thanks.

 

[Drej]

As far as I'm aware there is no integration function in Excel. The reason for this may be that in EXCEL it is really easy to integrate the function yourself using any of the standard integration schemes ("Midpoint", "Trapeziodal", etc.). Of course, once the integration procedure is setup in a spreadsheet, you will be able to use this for any subsequent functions you need to integrate.

-- drej --

 

[m777182]

Integration of a six order polynomial trend line(I am afraid that you will not be happy with the solution )should not be a problem: from algebra lessons we still remember(don't we?) that

integral(X^n* dx)=1/[a*(n+1)]*X^(n+1) for n<>-1; for n=-1 we get 1/a*ln(X)

with some effort you can make a simple Vba code for it.
m777182

 

[pmover]

awhile back in this forum, IRStuff recommended numerically integerating for another posting. seems to me that since the equation is available as is the data, numerically integrating is a simple process. check your math book or a good reference for proper application and check your results - the good old fashion way, by hand.

good luck!
-pmover