Curve Designer - Exponent Function for S-Curve

General discussion about Gig Performer
1

I’m trying to implement an S-Curve - centered around 0.5 - in Curve designed to mimic the logarithmic behaviour of a fader where you have more control around 0.

Curve equation I have found is the Logistic Function which requires a/(1+e^(-b(x-0.5)), however this definitely doesn’t look right in GP!

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My first thought was that ‘e’ should be ‘exp’ but that gives an incorrect formula error.

Tried various ways - including condensing down to a sigmoid of 1/1+e^-x - but still the same result.

Anyone know the proper way of doing an exponent? Or does anyone have an S-Curve equation in Curve Designer handy that they could please share?

Thanks!

2

Slight addendum - realised that it should be x-50, not x-5 and that a needs to be 100 rather than 1, and also that exp() works in the formula editor, which gives:

y = 100/(1+exp(-b*(x-50)))

With b set to 0.1 that gives this in curve designer:

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And this in Google Sheets using the same equation:

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So the equation is correct, just can’t get Curve Designer to do it…

Obviously could just use the Sheets output and smooth it, but an equation seems neater!

4

Maybe you should play with two points:

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5

I’ve managed to do it easily using the Sheets method and just adding a lot of points; the smooth function does a superb job!

So problem technically solved, but it still feels like either exponents don’t work or I’m not using the curve designed correctly, as that equation should work and allow the slope/centre to be adjusted by the a/b parameters