FindRoot and dealing with small numbers
- To: mathgroup at smc.vnet.net
- Subject: [mg47025] FindRoot and dealing with small numbers
- From: criticalheat at web.de (criticalheap)
- Date: Mon, 22 Mar 2004 05:18:34 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
I have got a problem concerning calculation with small numbers.
I want to solve an equation of the following kind:
equation := x - g(b) - f(x,b) == 0
and I want to plot the function h(b) = x, as a function of the
parameter b.
I use the following syntax:
FindRoot[equation , {x, {- 10^(-25), 10^(-30)}}, AccuracyGoal -> 15,
WorkingPrecision -> 16, MaxIterations -> 5000]
solnumerical := x /. %
N[solnumerical]
Now I have got 2 problems:
i) The line solnumerical := x /. % gives the error line:
ReplaceAll::"reps": "\!\({Null}\) is neither a list of replacement
rules nor \
a valid dispatch table, and so cannot be used for replacing."
ii) How can I teach mathematica to calculate with such small numbers.
He cuts every
number after the sixth decimal, which leads to wrong numerical
results.
for example hbar = 1.054571596 10^(-34) OUTPUT: (1.05457 10^-34) where
are the last digits ?
Thanks for your comment, Peter