[R] Determinant

chasiotisv at math.auth.gr chasiotisv at math.auth.gr
Thu May 14 10:44:10 CEST 2015


I am Vasilis Chasiotis and I am a candidate Ph.D. student in Aristotle  
University of Thessaloniki in Greece.

I have the following problem.

I want to check if the square of a number ( for example the square of  
1.677722e+29 ) is an integer.

The problem is that this number is the calculation of the determinant  
(so the number should be an integer) of a matrix 22x22, which means it  
has an approximation ( the "real" number is 1.6777216e+29 but R gives  
to me  1.6777215999999849e+29 ), because R use LU-decomposition to  
calculate the determinant.

That means that the radical of the number 1.6777215999999849e+29 is  
not an integer, but it should be.

How can we overcome this problem?

Thank you in advance.

I look forward to hearing from you soon.

Vasilis Chasiotis

More information about the R-help mailing list