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Re: Why isn’t the increase in frequen

  • To: mathgroup at
  • Subject: [mg95582] Re: Why isn’t the increase in frequen
  • From: dh <dh at>
  • Date: Thu, 22 Jan 2009 06:59:21 -0500 (EST)
  • References: <gl722n$cai$>

Hi Tia,

look e.g. at fpr1: there it says that you only want a result if t<per1. 

But in Manipulate, you multiply the time by "a" (not the frequency as 

you may have intended).

hope this helps, Daniel

ratulloch at wrote:

> Why isn't the increase in frequency/periodicity of this waveform not

> showing up tia sal2


> Greetings All


> I'm using the manipulate command to view what the wave form will look

> like will look like if I increase the frequency.

> But when I vary the variable =A1=A7a=A1=A8  to 3 the waveform only shows one

> complete wave instead of 3


> Example I vary the variable =A1=A7a=A1=A8 to 3 it should show 3 waveforms

> repeating but instead it shows just 1 waveform in 1/3 the time.


> Here=A1=A6s an image of what it's doing along with the code



> Here's the code below:


> tmin:=0

> tmax:=2 Pi

> per1=Pi;

> startPer1=0;

> fpr1[t_]:={Sin[Mod[t-startPer1,per1]+startPer1],startPer1<t<per1}


> per2=2 Pi;

> startPer2=Pi;

> fpr2[t_]:={.3*Sin[Mod[t-startPer2,per2]+startPer2],startPer2<t<per2}


> Manipulate[test=choice[Piecewise[{fpr1[(a*2 Pi)*(t-(phase/360/a))],fpr2

> [(a*2 Pi)*(t-(phase/360/a))]+c}],{t,tmin,tmax}],{{tmax,1,"t Time

> Scale"},0,5 Pi,1,Appearance=84_"Labeled"},{{a,1,"a Repeat Signal CPS"},

> 0,1000,1,Appearance=84_"Labeled"},{{phase,0,"Phase in degrees"},

> 0,-360,.5,Appearance=84_"Labeled"},{{c,0,"Offset C"},

> 0,-294,1,Appearance=84_"Labeled"},{choice,{Plot,Expand}}]


> The reason why I'm doing this is that when I do periodic interpolation

> the

> Formula breaks down due to the Gibbs Phenomenon.  The signals I'm

> creating have

> about 200 separate values thats why it breaks down.  But I'm using a

> simple example to see if it can be done.  So I can basically stitch

> multiple simple wave signals together to create one big complex one

> and

> still have the ability to increase the frequency of the complex signal

> over time.


> Is there another way I should be doing this?  I'm open to all

> suggestions


> Tia sal2


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