Re: Can't make function periodic for t<0
- To: mathgroup at smc.vnet.net
- Subject: [mg119326] Re: Can't make function periodic for t<0
- From: Heike Gramberg <heike.gramberg at gmail.com>
- Date: Mon, 30 May 2011 07:47:39 -0400 (EDT)
You can provide an offset for Mod. For example, Mod[a,L,b] will return values between b
and L+b. In your example, you could redefine mekeper according to
makeper[f_,L_,offset_] := f[Mod[#,L,offset]]&
then
x1=makeper[x,1,-1/2]
would be the periodic function you're looking for.
Heike.
On 30 May 2011, at 11:35, yitzhakbg wrote:
> This is the function to make periodic:
> x[t_] := Piecewise[{{-1, -1/2 <= t < 0}, {1, 0 <= t < 1/2}}]
>
> I saw DH's lovely post from 1/14/09:
> "if we want some function f to have period L we may define an operator:
> makeper[f_,L_]= f[Mod[#,L]]&
> Here is an example. We want a sine with period 1:
> sin1= makeper[Sin,1]"
> I can't get it to work for t<0 because Mod always returns positive values.
> Can anyone kindly help?
> Yitzhak
>