Difference between loops and vectorization
Santosh Srinivas wrote:
A fundamental question ...I'm trying to understand the differences between loop and vectorization ... I understand that it should be a natural choice to use apply / adply when it is needed to perform the same function across all rows of a data frame. Any pointers on why this is so? Unable to find the right reading place on the WWW which explains the concept.
Strange. "loop vectorization" gives a few hundred of hits, that tell you that loops are not as bad in R (compared to S) in many cases. "apply" is probably the least important vectorization method in R, but I admit that some texts make us believe that it is the point where you show your R-talents. "adply" is different: it is a rather complex function from package plyr by Hadley Wickham. This package provides some elegant orthogonal functions under a unified concept. I found it appealing at the first look, but I am less frequently using it nowadays because it can be terribly slow. Try the chapter in http://www.burns-stat.com/pages/Tutor/R_inferno.pdf Dieter
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