[PD] Getting a signal's slope

[Frank Barknecht]

Hi,
does anyone know, how I could derive the slope of a signal? For
example, if I have an osc~ and I want to delay the rising portion
depending on the current slope of the signal, how to do this. Or more
general, is there a way to get the derivative of a signal? 

I tried something like "fexpr~ $x1[2]-$x1[1]" but that gave me only a
stream of "0"s when printed out with print~, even if I feed it a
phasor~, which never has two values the same in its signal vector, so
the fexpr~ expression should never be zero.

Being a bit at loss,
-- 
 Frank Barknecht                               _ ______footils.org__