# [PD] Vanilla replacement for tanh~

Pagano, Patrick pat at digitalworlds.ufl.edu
Fri Jul 3 16:55:16 CEST 2015

```The tanh~.pd is working swell.
Would you all be able to suggest a replacement for the lp8_cheb~? I needed to replace three non-vanilla items
1.) tanh~
2.) make symbol [zexy]
3.) lp8_cheb~

I am trying to convert an algorithmic patch by a gentleman named Scott Norlund and these are the only problems from a rather couple patch.

Also, is there a work-around for "inits"?
Thank you all very much for the wonderful help

Sent from my iPhone

On Jul 3, 2015, at 2:44 AM, i go bananas <hard.off at gmail.com<mailto:hard.off at gmail.com>> wrote:

yes, you need to use a [clip~ -3 3] to restrict the input.  But the function converges to +0.999999 and -0.999999 or whatever by then anyway, so for all practical purposes it is fine.

On Fri, Jul 3, 2015 at 2:26 PM, Miller Puckette <msp at ucsd.edu<mailto:msp at ucsd.edu>> wrote:
I've never seen that approximation before but there must be some
restriction on the allowable values of X since the expression diverges
for large positive or negative values of x, while tanh(x) converges to
+1 nad -1, respectively.

cheers
Miller
On Fri, Jul 03, 2015 at 01:23:29PM +0900, i go bananas wrote:
> there's a good approximation for tanh that can be made using just a couple
> of simple arithmetic objects:
>
> formula is:  tanh(x) ~= x*(27+x*x) / (27+9*x*x)
>
> it's close enough for every application i've ever come across, it's cheap
> cos it only uses simple arithmetic, and it doesn't degrade the resolution
> of your signal like a table lookup does.
>
>
>
> On Fri, Jul 3, 2015 at 12:56 PM, Chris McCormick <chris at mccormick.cx<mailto:chris at mccormick.cx>> wrote:
>
> > On 03/07/15 03:06, Pagano, Patrick wrote:
> > > Is there a way i can replace something for tanh~
> > > and inits in Vanilla 46?
> >
> > Using a pre-computed table for speed:
> >
> > https://github.com/chr15m/blockhead/blob/master/e_tanh.pd
> > https://github.com/chr15m/blockhead/blob/master/e_tanh-help.pd
> >
> > Or install "blockhead" using deken. :)
> >
> > Cheers,
> >
> > Chris.
> >
> > --
> > http://mccormick.cx/
> >
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