Math Forum Discussions

N Kinoshita

Posts: 3
Registered: 12/7/04

InterpolatingFunction
Posted: Oct 7, 1996 1:59 AM

Plain Text

I have a question about using a InterpolatingFunction obtained
by NDSolve as a usual function.

I posted similar questions ealier last month, and received
much help to which I am very grateful.

First I ran:

NDSolve{c'[k]==...,w'[k]==...,c[ks]==cs,w[ks]==ws},{c,w},{k,ks,k0}]

Then I got:

{{c->InterpolatingFunction [...], w->InterpolatingFunction [...]}}

Next I ran, using the above result:

NDSolve[{k'[t]==0.715c[k[t]]+... /. %..%[[1]],k[0]==0.3},k,{t,0,40}]

Then I successfully (with the helpful suggestions from MathGroup) got

{{k->InterpolatingFunction [...]}}

Now there is a problem that I can not solve.
I want to look at how c[k[t]] moves as t moves from 0 to 40.

I found in page212 of the last edition of 'Mathematica' book
the following command and tried it.

k /. First[%]

which allowed me to plot k[t] by:

Plot[%[t],{t,0,40}]

When I similarly tried to plot c[k[t]] by:

Plot[%%%%[%[t],{t,0,40}]
^this is supposed to mean c[k] obtained by
c/. First[%]
immediately after getting {c->InterpolatingFunction[ ]}

Then I got a very strange looking plot together with some
error messages.

Can anybody suggest what went wrong?

Noriaki Kinoshita
University of Cambridge