Re: FindRoot in 5.0
- To: mathgroup at smc.vnet.net
- Subject: [mg42835] Re: FindRoot in 5.0
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Wed, 30 Jul 2003 19:30:26 -0400 (EDT)
- Organization: Universitaet Leipzig
- References: <bg7vqq$hj5$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
func[x_?NumericQ]:=(y=x;NIntegrate[BesselY[1/2,s],{s,1/2,y}])
will fix the problem in version 5.0, and you many
use the StepMonitor option to show the progress
FindRoot[func[x]),{x,2,4}],StepMonitor:>Print[x]]
Regards
Jens
Eric Mockensturm wrote:
>
> I realize that FindRoot has changed but there seems to be a
> fundamental difference in it between pre-5.0 versions and 5.0 that
> breaks most of my notebooks. Maybe I've been following bad
> 'programming' practices all these years, but....
>
> Anyway, a simple illustration follows.
>
> In 4.2:
>
> In[7]:=func[x_]:=(y=x;NIntegrate[BesselY[1/2,s],{s,1/2,y}])
> In[8]:=FindRoot[(Print[x];func[x]),{x,2,4}]
> Out[8]={x\[Rule]3.04729}
>
> In 5.0:
>
> In[1]:=func[x_]:=(y=x;NIntegrate[BesselY[1/2,s],{s,1/2,y}])
> In[2]:=FindRoot[(Print[x];
> Out[2]={x\[Rule]4.}
>
> with errors...
>
> NIntegrate::nlim: s = x is not a valid limit of integration
>
> It seems that 5.0 is trying to evaluate func[x] symbolically before
> start to search for a root. How do I make a global change to this
> behavior. Does it have something to do with the HoldAll attribute?
> FindRoot was been HoldAll in 4.2, too.