Re: Unexpected "Invalid comparison" error when plotting function defined with a Condition pattern
- To: mathgroup at smc.vnet.net
- Subject: [mg69174] Re: [mg69165] Unexpected "Invalid comparison" error when plotting function defined with a Condition pattern
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Fri, 1 Sep 2006 06:40:21 -0400 (EDT)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
Clear[g];
g[x_?Positive] = x;
Plot[Abs[g[10^y]], {y, 1, 2}];
Clear[g];
g[x_] = x*UnitStep[x];
Plot[Abs[g[10^y]], {y, 1, 2}];
Bob Hanlon
---- Andrew Moylan <andrew.j.moylan at gmail.com> wrote:
> Hi,
>
> Please consider the following simple function, defined for positive x
> using a Condition pattern:
>
> g[x_ /; 0 < x] = x;
>
> When I try to plot this function in the following way:
>
> Plot[Abs[g[10^y]], {y, 1, 2}];
>
> I unexpectedly receive some "Less::nord : Invalid comparison with 10. +
> 0. I attempted" errors. Can anyone explain why this is, and how I
> should best prevent it?
>
> Relevant note:
> Both of the following different plots of g succeed with no errors:
> Plot[Abs[g[y]], {y, 1, 2}];
> Plot[g[10^y], {y, 1, 2}];
>
> Irrelevant note:
> In my actual application, the function g is more complicated and is
> complex-valued (hence my use of Abs); but the error is reproducable
> with the very simple real-valued function g as defined above.
>
> Thanks for any insight you might be able to give me on this.
>
> Cheers,
>
> Andrew
>