## Exponential Function

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Guys, I have a function that returns an exponential graph.  It starts at 0.4 falling to 0.2.  This works.  However the exponential starts at 0.4 falling slow and getting faster.  I want it to start at 0.4 falling fast and slowing down.

`test_var = (double)(0.2 * (1.0 / (1.0 + (exp(i))))) + 0.2;`

Thanks for the help guys.

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Last Edited: Mon. Feb 15, 2021 - 08:54 PM

Please can you upload a hand drawing that approximates the desired curve?

Starting from i -inf , any fall is slow.

abdulai wrote:

Please can you upload a hand drawing that approximates the desired curve?

Starting from i -inf , any fall is slow.

Last Edited: Mon. Feb 15, 2021 - 07:11 PM
This reply has been marked as the solution.

Why not use Excel?...then you can rapidly adjust the constants like k1exp(-k2t)  to get the exact shape you want?

Your curve looks rather 1/x like---maybe that is preferred? you can even use Excel* to compare them side-by-side.

Excel can also do a fit (built in--- just right-click on a plot line) to polynomials, exponential, etc, if you give it a bunch of desired points (select "show equation" option)

*or Open Office, which is a great freebie

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

avrcandies wrote:

Why not use Excel?...then you can rapidly adjust the constants like k1exp(-k2t)  to get the exact shape you want?

Your curve looks rather 1/x like---maybe that is preferred? you can even use Excel* to compare them side-by-side.

Excel can also do a fit (built in--- just right-click on a plot line) to polynomials, exponential, etc, if you give it a bunch of desired points (select "show equation" option)

*or Open Office, which is a great freebie

Thanks guys for the input.