[Scilab-users] Envelop of a noisy curve

[Tim Wescott]

Heh.  This is much better than my suggested method, both in speed and in
resulting in a well-defined envelope.  I'll have to remember it.

On Fri, 2015-04-24 at 21:03 +0200, Samuel Gougeon wrote:
> Hello,
> Le 24/04/2015 14:05, paul.carrico at free.fr a écrit :
> 
> > Dear All,
> > 
> > I am absolutly not familiar with "signal processing" field, so my question is probably naïve: how can I proceed to get the envelop curve (maximum values) of a non periodic noisy signal ?
> Here is an example and its result:
> x = linspace(0,20,300);
> y = exp((2-x)/5).*sin(x)+rand(x);
> 
> clf
> plot2d(x,y)
> e = gce();
> e = e.children;
> e.foreground = color("grey80");
> 
> d = diff(y) ./ diff(x);
> pmax = find(d(1:$-1)>=0 & d(2:$)<0)+1;
> pmin = find(d(1:$-1)<0 & d(2:$)>0)+1;
> // edges corrections
> if d(1)<0 then
>     pmax = [1 pmax]
> end
> if d($)<0 then
>     pmin = [pmin length(y)]
> end
> //
> plot(x(pmax),y(pmax),"r",x(pmin),y(pmin),"b")
> 
> Zooming on that shows in some places the limits of this naive
> approach, to be refine.
> 
> Regards
> Samuel
> 
> 
> _______________________________________________
> users mailing list
> users at lists.scilab.org
> http://lists.scilab.org/mailman/listinfo/users

-- 

Tim Wescott
www.wescottdesign.com
Control & Communications systems, circuit & software design.
Phone: 503.631.7815
Cell:  503.349.8432