I just found out that the function "delayedAssign" is what I was looking
for.
2014-04-16 16:51 GMT+02:00 Luca Cerone <luca.cer...@gmail.com>:
> Hi Jeff,
> thanks for your reply.
>
> I read about it in the documentation and I plan to build the functions to
> download the csv and convert to rda in the future.
> At the moment, however, I am looking for a quick and dirty solution to
> lazy load the files I already have.
> (I know I could convert them straight to .rda files and will do it, I am
> using the occasion to learn some other
> way to do it).
>
> For example I have tried doing something like
>
> lazyLoadFun <- function(path){
> ds <- NULL
> read.data <- function(){
> if (is.null(ds)){
> message("importing dataset the first time")
> ds <- read.csv(path)
> } else {
> message("using cached copy of the dataset")
> }
> return(ds)
> }
> return(read.data)
> }
>
> get.italian.cities <-
> lazyLoadFun(system.file("extdata/italian_cities.csv"))
>
>
> In the functions where I need to use italian_cities I then do:
> italian_cities <- get.italian.cities()
> The first time I use get.italian.cities the file is loaded and cached into
> "ds", while the other time the cached variable "ds" is retrieved.
>
> The problem is that R doesn't pass variables by reference, so that ds is
> copied into italian_cities, which makes things quite slow for big datasets
> and makes using cached data useless.
>
> I am figuring out, for example, if it is possible to use "assign" and
> avoid copying the data into italian_cities.
>
> Thanks again for your reply, I will definitively look into .rda files!
>
> Luca
>
>
> 2014-04-16 15:39 GMT+02:00 Jeff Newmiller <jdnew...@dcn.davis.ca.us>:
>
> The standard way to put data into a package is to convert it to RDA as
>> described in the Writing R Extensions document. This is faster and more
>> compact than CSV.
>>
>> ---------------------------------------------------------------------------
>> Jeff Newmiller The ..... ..... Go
>> Live...
>> DCN:<jdnew...@dcn.davis.ca.us> Basics: ##.#. ##.#. Live
>> Go...
>> Live: OO#.. Dead: OO#.. Playing
>> Research Engineer (Solar/Batteries O.O#. #.O#. with
>> /Software/Embedded Controllers) .OO#. .OO#.
>> rocks...1k
>>
>> ---------------------------------------------------------------------------
>> Sent from my phone. Please excuse my brevity.
>>
>> On April 16, 2014 5:10:03 AM PDT, Luca Cerone <luca.cer...@gmail.com>
>> wrote:
>> >Hi, in a package I am developing some functions need to use some
>> >external
>> >data.
>> >I have these data as a set of .csv files that I have placed in the
>> >inst/extdata folder.
>> >
>> >At the moment I have a file "db-internal.r" where I load all the
>> >internal
>> >databases that could be used by the functions in my package;
>> >and assign them to some global (to the package) variables (all with the
>> >prefix db_ in front of them)
>> >For example (I didn't come out with a better name, sorry)
>> >
>> >db_italian_cities = read.csv(system.file("extdata/italian_cities.csv")
>> >
>> >like this I can use db_italian_cities in my functions.
>> >
>> >Some of these datasets are quite big and really slow down loading the
>> >package, plus for some of the task the package is meant to solve they
>> >might
>> >not even be required.
>> >I would like to be able to lazyload these datasets only when needed,
>> >how
>> >can I possibly achieve this without creating special databases?
>> >
>> >Some of them could change, so I intend to be able to download the most
>> >recent ones through a function that ensure the package is using the
>> >most
>> >recent version,
>> >so I would really prefer to simply use csv files.
>> >
>> >Thanks a lot in advance for the help!
>> >
>> >Cheers,
>> >Luca
>> >
>> > [[alternative HTML version deleted]]
>> >
>> >______________________________________________
>> >R-help@r-project.org mailing list
>> >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.
>>
>>
>
>
> --
> *Luca Cerone*
>
> Tel: +34 692 06 71 28
> Skype: luca.cerone
>
--
*Luca Cerone*
Tel: +34 692 06 71 28
Skype: luca.cerone
[[alternative HTML version deleted]]
______________________________________________
R-help@r-project.org mailing list
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.
