Re: Step Info from NDSolve

• To: mathgroup at smc.vnet.net
• Subject: [mg33648] Re: Step Info from NDSolve
• From: "Allan Hayes" <hay at haystack.demon.co.uk>
• Date: Thu, 4 Apr 2002 19:40:14 -0500 (EST)
• References: <a8g34f\$b2p\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```"Brian Higgins" <bghiggins at ucdavis.edu> wrote in message
news:a8g34f\$b2p\$1 at smc.vnet.net...
> Hi Mathgroup,
>  Is there anyway to get step information (number of steps, step size)
> from NDSolve during the actual integration

Brian,

The following trick is generally applicable:

If a print out of progress is sufficient,

h[(x_)?NumberQ, fx_, rhs_] := (Print[{x, fx}]; rhs)

NDSolve[{f'[x] == h[x, f[x], 2*f[x]],  f[0] == 1}, f, {x,0, 1}]

If you want data to work on then

g[(x_)?NumberQ, fx_, rhs_] :=  (points = Append[points, {x, fx}]; rhs)

points = {};
NDSolve[{f'[x] == g[x, f[x], 2*f[x]],  f[0] == 1}, f, {x, 0, 1}]

--
Allan

---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565

```

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