Existence of non-vectorised functions
Thanks to Uwe Ligges and Ben Bolker for their responses. My main concern was with the fact that R doesn't issue a warning when the user attempts an "if" test with a vector argument. Splus (at least Splus 6) does do this, saying that only the first element is used in testing the condition. I feel that R should also give this warning. thanks again, Ravi. ----- Original Message ----- From: "Uwe Ligges" <ligges at statistik.uni-dortmund.de> To: "Ravi Varadhan" <rvaradha at jhsph.edu> Cc: <r-help at stat.math.ethz.ch> Sent: Tuesday, November 26, 2002 12:43 PM Subject: Re: [R] Existence of non-vectorised functions
Ravi Varadhan wrote:
Dear R-Group: Recently, I ran into a problem. I was using a function called "I.1", which evaluates the first-order modified Bessel function of the first kind, in the package "CircStats". This function is not vectorized, since it uses a couple of "if" conditions. However, when I called this function with a vector argument, I got no error/warning messages in R1.5.1 (under Windows 2000). Furthermore, the results were generally incorect (please see the attached results). However, if I vectorized it using "ifelse" everything is fine (I created a function called "myI.1" to do this). I was wondering if there are functions in other packages, where such problems exist due to non-vectorization?
That's extremely probable. It depends on the package author and the complexity of the problem, thus you have to check it yourself whether it works vectorized or not, e.g. in the help files. BTW: You might want to send your improvements of I.1() to the package author as well (or even at first - hint, hint) ... Uwe Ligges
thanks, Ravi. #######################################################
require(CircStats) I.1(1:10)
[1] 0.5651591 1.5906369 3.9533702 9.7594643 24.3351955 [6] 61.3232698 155.7162813 396.4825232 1005.2747089 2517.6347571
myI.1(1:10)
[1] 0.5651591 1.5906369 3.9533702 9.7594652 24.3356418 [6] 61.3419369 156.0390965 399.8731348 1030.9147087 2670.9883206
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