How do I find an best fit equation in the form y=Ae^kx?

[Nadia]

I have a set of data, and the only line of best fit that is important to me
is in the form y=Ae^-kx. There are no negative or zero values in my data. I
know how to add the exponential trendline on the graph, but I want to be able
to do this function non-graphically. The LOGEST function seems to be very
close to what I need except that it fits lines to the exponential curve
y=b*m^x, so that m can change while there is no variable in front of x. Is
there anyway to modify the LOGEST function to meet my needs? OR is there
another function that would perhaps work better? Thank you.
Nadia

 

[Michael R Middleton]

Nadia -

The b in the LOGEST function is the same as the A in your function.

The m in the LOGEST function is the same as the e^-k in your function.

So the k in your function equals -LN(m), using the m from the LOGEST
function.

- Mike

www.mikemiddleton.com

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I have a set of data, and the only line of best fit that is important to me
is in the form y=Ae^-kx. There are no negative or zero values in my data. I
know how to add the exponential trendline on the graph, but I want to be
able to do this function non-graphically. The LOGEST function seems to be
very close to what I need except that it fits lines to the exponential curve
y=b*m^x, so that m can change while there is no variable in front of x. Is
there anyway to modify the LOGEST function to meet my needs? OR is there
another function that would perhaps work better? Thank you. Nadia