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Re: Graphing Difference Equation
*To*: mathgroup at smc.vnet.net
*Subject*: [mg91426] Re: [mg91393] Graphing Difference Equation
*From*: Bob Hanlon <hanlonr at cox.net>
*Date*: Thu, 21 Aug 2008 04:15:53 -0400 (EDT)
*Reply-to*: hanlonr at cox.net
For difference equations use RSolve
In[1]:=
Clear[y];
In[2]:=
y[t_] = y[t] /.
RSolve[{
y[t] == (3*y[t - 1] - y[t - 2])/2,
y[0] == 0, y[1] == 1},
y[t], t][[1]] //
Simplify
Out[2]=
2 - 2^(1 - t)
In[3]:=
{y[0], y[1]}
Out[3]=
{0,1}
In[4]:=
Plot[y[t], {t, 0, 20}, PlotRange -> All]
Bob Hanlon
---- Walkman <uvnarae at hotmail.com> wrote:
=============
Dear Group.
I have a trouble in graphing differece equation using mathematica.
For instance, I get a difference equation,
y_{t} = 1.5y_{t-1} - .5y_{t-2} = 0
Since I don't know how to input the code for graphics and just want
to check how the graph looks like,
I input the solution instead, A(-1.2)^t + B(.5)^t where A and B
constants
For simplicity, I choose A = B = 1.
Plot[(-1.2)^t + (.5)^t,{t,0,20}]
The problem is that it doesn't work at all.
If anyone who know exact way to graph difference equation, plz
tell me.
Thanks in advance.
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