# Re: [R] precision problem

From: Omar Lakkis <uofiowa_at_gmail.com>
Date: Thu 26 May 2005 - 01:07:37 EST

all.equal is helpful when I am comparing equality of two matrices. However, when I am comparing two individual number with > or < is my best bet doing if( abs(x - y) < tolerence) or is there a function like all.equal that has the same default tolerence?

On 5/25/05, Omar Lakkis <uofiowa@gmail.com> wrote:
> Thank you all.
> all.equal is very helpful since I am also interested in finding the
> mismatched prices.
>
> On 5/25/05, John Fox <jfox@mcmaster.ca> wrote:
> > Dear Omar,
> >
> > Perhaps I'm missing something, but why not just subtract one matrix from the
> > other and test the difference in relation to the precision that you require
> > for the comparison? E.g., to test near equality, something like, abs(A - B)
> > < 1e-13.
> >
> > I hope this helps,
> > John
> >
> > --------------------------------
> > John Fox
> > Department of Sociology
> > McMaster University
> > Hamilton, Ontario
> > 905-525-9140x23604
> > http://socserv.mcmaster.ca/jfox
> > --------------------------------
> >
> > > -----Original Message-----
> > > From: r-help-bounces@stat.math.ethz.ch
> > > [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Omar Lakkis
> > > Sent: Wednesday, May 25, 2005 9:09 AM
> > > To: r-help@stat.math.ethz.ch
> > > Subject: [R] precision problem
> > >
> > > I have prices that I am finding difficult to compare with ==,
> > > > and >, due to precision. For example: the numbers should
> > > match, with '==', but they differ in the magnitude of 1e-14
> > > due to bunch of calculations that I run on them. Programming
> > > with java, I am used to implementing a function that compares
> > > the difference between the numbers to a pre determined
> > > precision factor. This could be very slow when I have two
> > > matrices of numbers that I could otherwise compare with a
> > > simple '==', '>' or '<' in R.
> > > What is teh best solution for this problem?
> > > Can I control the precision of ==, > and < without having to
> > > reimplement the operations in a slow way?
> > >
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