Of course the number _is_ an integer. It seems you are asking whether that integer can be exactly _represented_ on a computer? That depends on your processor (eg. 32/64 bit) and the size of the number; alternatively you could calculate with arbitrary precision with the Rmpfr package.
For more insights, have a look at Pat Burs' summary of number representation in R (http://www.burns-stat.com/documents/tutorials/impatient-r/more-r-key-objects/more-r-numbers/) and/or read chapter one of his R inferno. Or, maybe you can state more clearly what you are trying to achieve in the end, there might be other options. Cheers, B. On May 14, 2015, at 4:44 AM, chasiot...@math.auth.gr wrote: > Hello, > > 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 > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.