Re: Plotting
- To: mathgroup at yoda.ncsa.uiuc.edu
- Subject: Re: Plotting
- From: ags at seaman.cc.purdue.edu (Dave Seaman)
- Date: Wed, 27 Feb 91 13:27:44 -0800
mkende at athena.mit.edu writes:
>I have a question concerning plotting. I am using release 1.0 on a Next
>station. My question is as follows. I have some equation like this:
>
>1 -2x -y
>
>which I get from differentiation. I then solve for x in terms of y:
>
>Solve[% == 0,x]
>
>to get
>
>{x->1-y}
> ---
> 2
1 - y
When I do this, I get {{x -> -----}}. The extra set of braces makes a
2
difference.
>
>I want to plot x as a function of y. If I use the standard plot, i.e.
>
>Plot[%,{y,0,1}]
>
>I get an error. Any other way I can think of, namely making a function of the
>right hand side of the answer using some variant of "/. %" , still gives the
>same error.
If you use Plot[x /. %,{y,0,1}], Plot complains that "x /. %" does not evaluate
to a real number. That's because you get {(1-y)/2}, which is a list, rather
than a real number.
>Is there any way of plotting (1-y)/2 from the solution without having to simply
>retype it into the Plot command?
You can use
Plot[First[x /. %],{y,0,1}]
Dave Seaman