On Wednesday, 21.03.2007 at 14:07 +0800, Berwin A Turlach wrote: > > All help/suggestions/appreciated! > > The calculations are done in floating point arithmetic, not integer > arithmetic. From the help page on `choose' one might already guess > so much, but reading "R-2.4.1/src/nmath/choose.c" definitely confirms > this fact. > > Thus, your problem is covered by FAQ 7.31: > > http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f
Thanks Berwin. OK, I understand the problem now. I was wondering if it something along those lines, but initially dismissed that as a possibility since I expected 'choose' to be an integer calculation. However, the underlying problem that gave rise to the difficulty was as follows. A colleague wishes to create a matrix, where one of the dimensions of the matrix is the result of the 'choose' function, i.e. mycols<-choose(11,6) a_matrix<-matrix(0,nrow=11,ncol=mycols) Clearly, 'ncol' casts mycols as as integer. In this case, a_matrix has only 461 columns, not 462. What's the best way to make this work as required? Dave. -- Dave Ewart [EMAIL PROTECTED] Computing Manager, Cancer Epidemiology Unit Cancer Research UK / Oxford University PGP: CC70 1883 BD92 E665 B840 118B 6E94 2CFD 694D E370 Get key from http://www.ceu.ox.ac.uk/~davee/davee-ceu-ox-ac-uk.asc N 51.7518, W 1.2016
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