[EXCEL] Calculate squares of difference of 2 functions

[Hermanator]

Hello all,

I have made an Excel sheet that I use to fit some measurement data to a theoretical model. The model is a bit too complicated to fit it automatically, so I fit it manually by tuning a number of parameters.

I would like to have a cell display a value as a measure of the accuracy of the fit. I think that the best way to do this is to calculate the "sum of the squares of the difference". Many fitting procedures work by minimizing this sum of the squares (least square fitting). However, I have not been able to find a function that can calculate this number at once. Another problem is that the data-points of measurement and fit are not necessarily the same.
For instance; I this case measurement data of current-voltage could be at V=0, V=0.5, V=1 etc. while the fit data-points would be at V=0, V=0.1, V=0.2. Another time, the measurement data could be at different intervals. This makes it very difficult to calculate the value manually.

Is there an Excel function that can calculate the accuracy of a fit, even when the data points are not equal?

 

[xlhelp]

Have you looked at DEVSQ or STDEVP functions under help?

If you use DEVSQ then you will need to find the Square Root of the average of DEVSQ


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