Thank you. May I ask, what would you recommend reading in order to learn how to vectorise loops with dependencies using data.table facilities? I have been searching online on this topic since last night but no luck yet.
-------------------------------------------- On Thu, 5/28/15, David Winsemius <dwinsem...@comcast.net> wrote: Subject: Re: [R] Using lapply when there are dependencies Cc: r-help@r-project.org Date: Thursday, May 28, 2015, 7:02 AM On May 27, 2015, at 4:34 PM, blue honour via R-help wrote: > Hi all, > > Let's say I have a vector: > > vv<-c(1,2,3) > > > And suppose I have a function f(a,b), which is a function of 2 scalar inputs. I would like to evaluate this function separately for each element of the vv vector while the second input to f( ) will be the previous output from f( ). So, the valuation of f() has a dependency on the previous f( ) valuation (recursive). This type of calculation is easy to set up with a for loop but that will run slow. How can I achieve this with apply family of functions please? The speed of loops is determined by the speed of their inner functions. The Reduce() function does what you request but for the application described it will need an init value. Reduce(f, vv, init=<something>) > I have the same question for the case when vv is a data.table instead of a vector. I could be wrong but that doesn't sound like an effective use of the data.table facilities. -- David Winsemius Alameda, CA, USA ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
