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Re: How to express this function.

• To: mathgroup at smc.vnet.net
• Subject: [mg84240] Re: How to express this function.
• From: mark <markmgg at googlemail.com>
• Date: Fri, 14 Dec 2007 23:18:26 -0500 (EST)
• References: <fjunch$27q$1@smc.vnet.net>

On Dec 15, 12:00 am, "huxiaopengs... at gmail.com"
<huxiaopengs... at gmail.com> wrote:
> f is  a period continual function with period  1.
> f equals x when 0<x1/2,equals -x when -1/2<x<1.
>
> How to express this function?

The function "Which" will do that for you.

The problem is when f equals x, the condition wasn't clear (I mean
0<x1/2) but I will use the following example to illustrate the method,
and then you will have do some changes to suite your problem:

In[1]:= f[x_] := Which[-1/2 < x < 0, -x, 0 < x < 1/2, x]

In[2]:= f[1/4]

Out[2]= 1/4

In[3]:= f[-1/3]

Out[3]= 1/3