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Re: Can't make function periodic for t<0

  • To: mathgroup at smc.vnet.net
  • Subject: [mg119356] Re: Can't make function periodic for t<0
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Tue, 31 May 2011 07:49:54 -0400 (EDT)

ClearAll[x, makeper]
x[t_] := Piecewise[{{-1, -1/2 <= t < 0}, {1, 0 <= t < 1/2}}]
makeper[f_, p_, d_][t_] := f[Mod[t, p, d]]
Plot[x@t, {t, -5, 5}, PlotRange -> {-1, 1}]
Plot[makeper[x, 1, -1/2]@t, {t, -5, 5}, PlotRange -> {-1, 1}]

Plot[Cos@t, {t, -5, 5}, PlotRange -> {-1, 1}]
Plot[makeper[Cos, 1, -1/2]@t, {t, -5, 5}, PlotRange -> {-1, 1}]

Bobby

On Mon, 30 May 2011 05:35:39 -0500, yitzhakbg <yitzhakbg at gmail.com> 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
>


-- 
DrMajorBob at yahoo.com


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