mattyo

I'm trying to put an s-curve into a buffer~ to use as a lookup table, 

but I can't figure out the damn math. I gather the formula to use 

b being a curve constant, & a shifting it. I was trying to peek into 

a buffer using [expr 1. / 1. + exp(($f1*$f2) - $f3)] my curve 

rockets up, but never levels out at the top.

Can someone who understands math tell me what I'm doing wrong?

I'm trying to put an s-curve into a buffer~ to use as a lookup table,  
but I can't figure out the damn math.  I gather the formula to use  
would be: y= 1./ 1 + exp((b*x) -a)

b being a curve constant, & a shifting it.  I was trying to peek into  
a buffer using [expr 1. / 1. + exp(($f1*$f2) - $f3)]  my curve  
rockets up, but never levels out at the top.

math-is-over-my-head

Couple of parentheses should clear things up:

Right now you're adding 1/1 to exp(($f1...etc., so it will never level 

out. (because the exp. is going to keep growing in value.) Once you 

add the parentheses, you should see the expected asymptotic behavior.

Right now you're adding 1/1  to exp(($f1...etc., so it will never level 
out. (because the exp. is going to keep growing in value.)  Once you 
add the parentheses, you should see the expected asymptotic behavior.

On around Mar 6, 2006, at 4:04, mattyo said something like:

> Can someone who understands math tell me what I'm doing wrong?

Peter McC. answered your top-level question. But if you're really 

having a hard time with the math, you might want to take a look at 

lp.scampf from Litter Power, which is there particularly for creating 

S-shaped and other shaped-curves, doing all the hard math for you. Just 

play with the number boxes in the help file until you get the shape you 

Here's a snapshot showing what it looks like:

I've removed the alpha channel to see if that helps the folks who have 

been having problems viewing Max-generated TIFFs and colors are trimmed 

to 4-bit resolution to minimize bandwidth. Forum readers will probably 

have to download the Litter Starter Pack (URI below) to see it; sorry, 

| Litter Power & Litter Bundle for Jitter

pcastine@bek.no | iCE: Sequencing, Recording, and Interface Building

http://www.dspaudio.com/software/software.html

On around Mar 6, 2006, at 4:04, mattyo said something like:
> Can someone who understands math tell me what I'm doing wrong?

Peter McC. answered your top-level question. But if you're really 
having a hard time with the math, you might want to take a look at 
lp.scampf from Litter Power, which is there particularly for creating 
S-shaped and other shaped-curves, doing all the hard math for you. Just 
play with the number boxes in the help file until you get the shape you 
want.

I've removed the alpha channel to see if that helps the folks who have 
been having problems viewing Max-generated TIFFs and colors are trimmed 
to 4-bit resolution to minimize bandwidth. Forum readers will probably 
have to download the Litter Starter Pack (URI below) to see it; sorry, 
that's beyond my power to control.

math is over my head