[Rcpp-devel] Help with accessing and manipulating List objects

[Tal Galili]

Thank you Romain and Wush.

Where from can I get the latest version of Rcpp with these new features?
And how may I learn how to use them?

Many thanks,
Tal





----------------Contact
Details:-------------------------------------------------------
Contact me: Tal.Galili at gmail.com |
Read me: www.talgalili.com (Hebrew) | www.biostatistics.co.il (Hebrew) |
www.r-statistics.com (English)
----------------------------------------------------------------------------------------------



On Sun, Jul 21, 2013 at 12:48 PM, Romain Francois
<romain at r-enthusiasts.com>wrote:

> Hi Tal,
>
> I'm travelling right now, i'll give some additional pointers later.
>
> This is a nice non trivial example, and i hope that the code îve put in
> recently (with is<>) can help you so that you dont have to use TYPEOF for
> dispatching.
>
> Our exchange at useR is part of my motivation for adding this.
>
> Romain
>
> Le 20 juil. 2013 à 18:44, Tal Galili <tal.galili at gmail.com> a écrit :
>
> Hello dear Rcpp users,
>
> First - I'd like to say that I took Hadley and Romain's workshop at the
> useR conference this year, and I am very excited about trying out Rcpp -
> this project looks AMAZING.
>
> Second - this is my first post, and I apologize if my question is too
> basic. To my defense, I tried looking through this mailing list / googled
> before asking, and read through Hadley's github chapter on Rcpp.
>
> The questions:
>
> I am looking to understand better how List objects can be navigated, their
> elements accessed, and manipulated - using Rcpp.
>
> For example, here is an R list object:
>
> x <- list(a = 1, b = 2, c = list(ca = 3, cb = 4, 5), 6)
> attr(x[[1]], "type") = "fun"
> attr(x[[3]][[1]], "type") = "fun"
> x
>
> I would like to create two types of functions:
> 1) A function that will go through "x" and will *RETURN* all of the
> elements within it that are of type "fun".
> In R I would do it like this:
>
> return_fun <- function(x) {
>    fun_nubmers <- numeric()
>    for(i in seq_along(x)) {
>       if(class(x[[i]]) == "list") {
>          fun_nubmers <- c(fun_nubmers, return_fun(x[[i]]))
>       } else {
>          if(!is.null(attr(x[[i]], "type"))) {
>             if(attr(x[[i]], "type") == "fun") fun_nubmers <-
> c(fun_nubmers, x[[i]])
>          }
>       }
>    }
>    return fun_nubmers
> }
> return_fun(x) # output: 1 3
>
> But in Rcpp there are many parts to this R function that I don't know how
> to do. I don't know how to access the attributes of a sub-element within a
> List, I don't know how to check if that attribute is null or not, etc. So
> any suggestions on either reading material (or better yet - an example of
> how this function might be created in Rcpp would be great.
>
>
> 2) A function that will go through "x" and will *CHANGE* all of the
> elements within it that are of type "fun". For example, adding 1 to them.
> In R I would do it like this:
>
> add1_fun <- function(x) {
>    for(i in seq_along(x)) {
>       if(class(x[[i]]) == "list") {
>          x[[i]] <- add1_fun(x[[i]])
>       } else {
>          if(!is.null(attr(x[[i]], "type"))) {
>             if(attr(x[[i]], "type") == "fun") x[[i]] <- x[[i]] + 1
>          }
>       }
>    }
>    x
> }
> add1_fun(x)
> return_fun(x) # output: 1 3
> return_fun(add1_fun(x) ) # output: 2 4
>
>
> 3) Is it possible to work with some "global" variable from within a
> recursive Rcpp function?
> For example:
>
>
> count_till_5 <- function() {
>    if(!exists("global_var")) global_var = 0
>
>    if(global_var <5) {
>       global_var <<- global_var+1
>       count_till_5()
>    }
> }
> count_till_5()
> global_var
>
> Is there a way to create something like this with Rcpp?
>
>
> Thanks in advance for any help.
>
> With regards,
> Tal
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> ----------------Contact
> Details:-------------------------------------------------------
> Contact me: Tal.Galili at gmail.com |
> Read me: www.talgalili.com (Hebrew) | www.biostatistics.co.il (Hebrew) |
> www.r-statistics.com (English)
>
> ----------------------------------------------------------------------------------------------
>
>  _______________________________________________
> Rcpp-devel mailing list
> Rcpp-devel at lists.r-forge.r-project.org
> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.r-forge.r-project.org/pipermail/rcpp-devel/attachments/20130721/2cdda80d/attachment.html>