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.
