[R] precision problem

John Fox jfox at mcmaster.ca
Wed May 25 16:27:57 CEST 2005

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 Fox
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Omar Lakkis
> Sent: Wednesday, May 25, 2005 9:09 AM
> To: r-help at 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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