Decimal Accuracy Loss?
Thanks, Bert. That's a big help. -Brigid
On Wed, Apr 6, 2011 at 11:45 AM, Bert Gunter <gunter.berton at 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 <bkmooney at 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
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-- "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