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Does anybody know the maths behind the trend formula in Excel, I am needing to predict a expiry date based on the ware and tear of a part, but can't find a formula to do this. The excel trend function seems to be exactly what I'm after but I don't want to use an Excel plug in for my app. And besides it is always nice to know how these things work!
the function used by Excel it's Square Least Method (o minimos cuadrados, in spanish) and any statistic book like linear regression
the equation is Y=A+B*X
where
B=(n*Sum(X*Y)-Sum(X)*Sum(Y))/(n*Sum(X^2)-(Sum(X))^2)
A, is obtain solving the equation
A=(Yaverage-B*Xaverage)
and
n, the number of data
X, Y, the points
i hope you understand me
Also look in the Excel help for SLOPE function
That'll do nicely Sir!
It's at this point I wish I had paid more attention in maths!! Thanks for the answer, after a short pondering I now understand it.
Just in case anyway was too lazy to code it up...
i have uploaded a sample...