I am trying to create a function that will run an exponential regression for a range of data, my code thus far is as follows to figure out the A factor:
The formula I am using worked for me as an excel formula.
Any suggestions would appreciated!
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What worked for you as an Excel formula?
Entia non sunt multiplicanda sine necessitate
The's the a in y = a*m^xPlease Login or Register to view this content.
I will try the regression estimation using the power fit function y = a*m^x above too. I will see how close this fits the data sets. Thanks!
I was hoping to be able to estimate the a in the function y = a*exp^(b*x).
The excel formula I used to do this was = EXP(INDEX(LINEST(LN(yRange), xRange),1,2))
When the vba function runs it returns an 'Object required' error.
In Excel, an array function like {=ln(yrange)} will return an array of numbers. This kind of array syntax does not translate into VBA. In order to do this, you will need to do one of two things before calling the LINEST() function in VBA:
1) Add a helper column in the spreadsheet that will calculate the logs. In an adjacent column, a simple spreadsheet formula like =ln(B2) copied down will create another range. This "helper column" will then be used as yrange in VBA and passed to the LINEST() function.
2) Have a loop upstream of the Linest function that will store the logs in a VBA array. Something likeI would also point out that y=A*e^(bx) is equivalent to A*m^x where m=e^b, so the two regressions should be no different from each other.Please Login or Register to view this content.
Originally Posted by shg
A power function has the form y=a*x^m.
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