       Re: Simultaneous difference equation

• To: mathgroup at smc.vnet.net
• Subject: [mg30603] Re: Simultaneous difference equation
• From: "Orestis Vantzos" <atelesforos at hotmail.com>
• Date: Fri, 31 Aug 2001 04:09:28 -0400 (EDT)
• Organization: National Technical University of Athens, Greece
• References: <9mkt9m\$1vn\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Search for DSolve (and NDSolve, I suppose) in Help.
Plus, check the rules for writting code in Mathematica...
an equation of the form a_1*y(t)=a_2*x(t) is nonsensical in Mathematica..
a1 y[t]==a2 x[t] is much better.
Remember:
1) Anything with an underscore in it is a pattern... so a_1 is a pattern
called a that has head 1, for instance 1[argument], NOT the variable a1
2) = means assignment NOT equality... use ==
3) Functions are inputed with square brackets y[x]...NOT y(x) (which is just
y*x)
Orestis
PS. Sorry I'm not focusing on your main question, but if you don't take care
of your syntax you'll get annoyed really really soon, since you won't be
able to reproduce the examples in the Help files... ;-)
"Shusaku Yamamoto" <shusaku.yamamoto at buseco.monash.edu.au> wrote in message
news:9mkt9m\$1vn\$1 at smc.vnet.net...
> Hello, I have just started using (or more appropriately trying to use)
> Mathematica. As you expect, I have a problem. I would like to know
> Mathematica code for solving simultaneous difference eqation; for
> example:
>
> a_11*x(t)+a_12*y(t)=a_13*x(t-1)+a_14*y(t-1)+k_1
> a_21* x(t)+a_22*y(t)=a_23*x(t-1)+a_24*y(t-1)+k_2
>
> Or, in matrix notation,
>
> A_1*Y(t)=A_2*Y(t-1)+K
>
> t denotes time t, and t-1 is one period before time t.
>
> I have go through help menu in Mathematica. Yet, I could not get reached
> to the topic of difference equation. If you know the code (or what to be
> typed), could you reply this message?
>
> Thank you very much in advance.
>

```

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