       Re: newbie: how to define, typeset a multi-rule function?

• To: mathgroup at smc.vnet.net
• Subject: [mg96788] Re: [mg96767] newbie: how to define, typeset a multi-rule function?
• From: DrMajorBob <btreat1 at austin.rr.com>
• Date: Wed, 25 Feb 2009 04:01:44 -0500 (EST)
• References: <200902241046.FAA23629@smc.vnet.net>

```As you're not speaking "Mathematica", I have to do some guessing, but
perhaps this is the function you want:

Subscript[f, x][chi_] = Piecewise[{{k, 0 <= chi <= 1}}]

\[Piecewise]k	0<=chi<=1
0	True

or

Subscript[f, x][\[Chi]_]=Piecewise[{{k,0<=\[Chi]<=1}}]

\[Piecewise]k	0<=\[Chi]<=1
0	True

In the second version I used the "special characters" palette to enter
\[Chi].

To enter Subscript[f, x], just type f, then Ctrl-_x. (That does NOT make
the function depend on x. It simply makes x part of the function name.)

You can also copy/paste the first line to Mathematica, press Enter to
evaluate the line, and the bracketed version should appear.

> Once I've typeset this function, I want to actually solve it.

No clue what that means. In mathematics we solve equations/conditions...
not functions.

I might guess that you want to invert the function, but it's not
invertible, so... clarify what you want.

Bobby

On Tue, 24 Feb 2009 04:46:36 -0600, Tom Roche <tlroche at gmail.com> wrote:

> As advertised by the Subject:, I'm new to Mathematica (specifically
> 7.0.0 for Students for 32-bit Windows on XP Pro) so please excuse any
> lapses in terminology. I'd also appreciate pointers to specific docs
> rather than just an RTFM. I suspect in this case I just need to know
> what the appropriate term is for what I'm trying to create. However
> I've tried searching the docs for various permutations of multi-rule
> or multi-line function, and even googling, to no avail.
>
> I'm trying to create a notebook that typesets a particular
> mathematical function, and then solves it. The function has 2 parts or
> rules: it returns k (a constant) for one part of its domain, and 0
> otherwise. This is typically typeset with the function name and the
> equals sign on one line, then a large left curly bracket (or brace)
> centered on that line, then each rule on a separate line with all the
> rule lines to the right of the bracket. For an example in a math
> layout, I can almost typeset the function in OpenOffice Math like
>
> f_x(%chi) = left lbrace stack {k if %chi in [0,1] # 0 otherwise} right
> rbrace
>
> (except that I don't want the closing brace, but that's another
> problem). I tried to create this using the palettes, but I didn't see
> one that did multiline brackets. What do I need to use?
>
> Once I've typeset this function, I want to actually solve it. How does
> one create a function with multiple rules in Mathematica?
>
> TIA, Tom Roche <Tom_Roche at pobox.com>
>

--
DrMajorBob at longhorns.com

```

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