Thanks, Bert. That's a big help. -Brigid
On Wed, Apr 6, 2011 at 11:45 AM, Bert Gunter <gunter.ber...@gene.com> wrote: > Confirmed. "Casting" just adds/removes the dim attribute to the > numeric vector/matrix. > > -- Bert > > On Wed, Apr 6, 2011 at 8:33 AM, Brigid Mooney <bkmoo...@gmail.com> wrote: >> This is hopefully a quick question on decimal accuracy. Is any >> decimal accuracy lost when casting a numeric vector as a matrix? And >> then again casting the result back to a numeric? >> >> I'm finding that my calculation values are different when I run for >> loops that manually calculate matrix multiplication as compared to >> when I cast the vectors as matrices and multiply them using "%*%". >> (The errors are very small, but the process is run iteratively >> thousands of times, at which point the error between the two >> differences becomes noticeable.) >> >> I've read FAQ # 7.31 "Why doesn't R think these numbers are equal?", >> but just want to confirm that the differences in values are due to >> differences in the matrix multiplication operator and manual >> calculation via for loops, rather than information that is lost when >> casting a numeric as a matrix and back again. >> >> Thanks in advance for the help, >> Brigid >> >> ______________________________________________ >> R-help@r-project.org mailing list >> 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. >> > > > > -- > "Men by nature long to get on to the ultimate truths, and will often > be impatient with elementary studies or fight shy of them. If it were > possible to reach the ultimate truths without the elementary studies > usually prefixed to them, these would not be preparatory studies but > superfluous diversions." > > -- Maimonides (1135-1204) > > Bert Gunter > Genentech Nonclinical Biostatistics > ______________________________________________ R-help@r-project.org mailing list 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.
