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From: "John D'Errico" <woodchips@rochester.rr.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: significant digits
Date: Tue, 7 Aug 2007 13:34:20 +0000 (UTC)
Organization: John D'Errico (1-3LEW5R)
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"sunil vaidya" <sunil.vaidya@gmail.com> wrote in message 
<f99qoe$h6e$1@fred.mathworks.com>...
> i'm running a prog in matlab which uses two matrix
> inversions and one roots function. i have some inconsistency
> in my results. does matlab truncate numbers beyond 16
> significant digits? and if it does, is they any way around
> this problem----can the accuracy be increased or something? 
> TIA

I'll just add a few extra comments to what
Rick has ably explained. Very often we see
people looking for additional precision in a
numerical computation. They think, if only
I could just throw more digits at this, I could
solve my problem simply, without actually
investing any thought in it.

The flaw is, that logic never ends. We would
see people trying to use 100 digits of
precision to solve a problem where their
data only has 2 significant digits. (Yes, it
is easy enough to formulate a nasty
problem.) Garbage in, garbage out.

You will benefit far more from some study
of your problem, learning how to compute
efficiently and accurately what you need to
do in a reasonable amount of precision, than
you will from just throwing a few extra digits
at it.

HTH,
John