CHOP - controlling op parameter based on geo attribute

[cily]

Hey,

I've a chop network where I'm using a jiggle, I would like control a parameter of jiggle by a point attribute of my geometry.

doing this I imported my parameter as channel scoping out from the jiggle operator and using in that parameter this expression

chopi("px",$I) assuming to read the name of my channel (px) plus the index of that, or using cop("px", $I). but no one of these are working and I can not acces the index using $I.

do you know how to resolve this? or even do you have any jiggle example in chop vex?

thanks in anticipate.