       Re: What am I doing wrong with this code?

• To: mathgroup at smc.vnet.net
• Subject: [mg82545] Re: [mg82519] What am I doing wrong with this code?
• From: DrMajorBob <drmajorbob at bigfoot.com>
• Date: Wed, 24 Oct 2007 04:28:19 -0400 (EDT)
• References: <14846561.1193151252112.JavaMail.root@m35>

```It plots just fine at this machine (WinXP, Mathematica 6.0.1).

IIRC, v5.2 would complain about complex numbers arising from the second
function for y > 1. If that's the problem, you can split it in two plots
and Show the results, something like this:

Show[Plot[1/(1 + y^2), {y, 0, 5}], Plot[Sqrt[-1 + 1/y], {y, 0, 1}]]

or perhaps

Clear[f]
f[y_] /; y <= 1 := Sqrt[-1 + 1/y]
f[y_] = 0;
Plot[{1/(1 + y^2), f@y}, {y, 0, 5}]

Bobby

On Tue, 23 Oct 2007 04:32:30 -0500, sean_incali <sean_incali at yahoo.com>
wrote:

> I think I'm having a brain fart. Seriously...
>
> Plot[{1/(1 + y^2), (1/y - 1)^(1/2)}, {y,  0, 5}]
>
> What is wrong with that code? Maybe it's not solvable in mathematica?
>
> I'm trying to plot nullclines of a system of ODEs. and those function
> up there are them. I just can't get mathematica to plot them in the
> same graph.
>
> I get an error message saying...
>
>> From In:=
> (1/y - 1)^(1/2)  is not a machine-size real number at y =
> 1.0000001666666667`.
>
> Any help is appreciated.
>
> sean
>
>
>

--

DrMajorBob at bigfoot.com

```

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