If you multiply a matrix by its inverse you should get an identity matrix. In R, you get an answer that is accurate up to about 16 decimal points? Why can't one get a perfect answer? See for example: c(5,3)->x1 c(3,2)->x2 cbind(x1,x2)->x solve(x)->y x%*%y Vikas Rawal ============================================= This Mail was Scanned for Virus and found Virus free
Vikas Rawal wrote:> If you multiply a matrix by its inverse you should get an identity matrix. In R, you get an answer that is accurate up to about 16 decimal points? Why can't one get a perfect answer?Because R makes use of a digital computer which cannot work exactly using floating-point arithmetics ... Please read some textbook about a numerics and computers. Uwe Ligges> See for example: > > c(5,3)->x1 > c(3,2)->x2 > cbind(x1,x2)->x > solve(x)->y > x%*%y > > Vikas Rawal > > =============================================> > This Mail was Scanned for Virus and found Virus free > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html