Re: using a previous result

• To: mathgroup at smc.vnet.net
• Subject: [mg67351] Re: using a previous result
• Date: Mon, 19 Jun 2006 00:01:14 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```On 6/18/06 at 5:13 AM, ridley_david at yahoo.com wrote:

>Once I've solved a system of equations, I would like to use the
>previous results in future equations. If my output is
>{{p1->x,p2->y}} how do I assign those values as p1star and p2star so
>I can reuse them?

This will do what you want

{p1star,p2star}={p1,p2}/.First@{{p1->x,p2->y}}

But note often it isn't necessary to extract the values from rules. For example here is a root of a simple polynomial

In[17]:=
root=FindRoot[x^2-.5x-1,{x,0}]

Out[17]=
{x -> -0.7807764064044151}

Now this can be used to evaluate any expression of x say 2 x + 1 as follows:

In[18]:=
2 x+1/.root

Out[18]=
-0.561553

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