[R] Referencing a component of a large object (Error: slot NULL)

[William Dunlap]

  tf <- vector("list", numberofchains)
  for (j in 1:numberofchains){
      s <- paste("'chain:",j,"'" ,sep="")
      tf[[j]] =  mi.control.i at data$s at variables$y.obs.tx at parameters[30,]
  }


If you want the component whose name is the value of the variable 's'
use data[[s]].

The syntax 'data$s' means to get the component of 'data' called "s",
usually the same as 'data[["s"]]'.


Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Fri, Aug 28, 2015 at 12:08 PM, Andrea Lamont <alamont082 at gmail.com>
wrote:

> I am running a simulation and need to refer to a matrix of parameters from
> a large object. Here is a snippet of the object structure itself:
>
> Formal class 'mi' [package "mi"] with 3 slots
>   ..@ call       : language .local(y = y, n.chains = ..2, max.minutes =
> 20000)
>   ..@ data       :List of 100
>   .. ..$ chain:1  :'data.frame':    10000 obs. of  76 variables:
> Formal class 'missing_data.frame' [package "mi"] with 17 slots
>   .. .. .. ..@ .Data       : list()
>   .. .. .. ..@ variables   :List of 76
>   .. .. .. .. ..$ y.obs.tx:Formal class 'binary' [package "mi"] with 27
> slots...
>
> The parameter list I need can be referenced by:
>
> mi.control.i at data$'chain:1'@variables$y.obs.tx at parameters[30,]
>
> Since this is a simulation, I would like to grab the parameters from each
> chain and join them together in a matrix. I have this:
>
> tf <- vector("list", numberofchains)for (j in 1:numberofchains){
>   s <- paste("'chain:",j,"'" ,sep="")
>   tf[[j]] =  mi.control.i at data$s at variables$y.obs.tx at parameters[30,]}
>
> Within the loop, however, the reference to the object (tf[[j]]) does not
> work. I get an error that reads
>
> Error: trying to get slot "variables" from an object of a basic class
> ("NULL") with no slots
>
>
> I am happy to send reproducible code, however, I obtain this object through
> the package 'mi' and is computationally intensive. I'm not sure if it makes
> it easier for folks. Let me know.
>
> Any ideas?
>
> --
> Andrea Lamont, PhD
> Post-Doctoral Fellow
> University of South Carolina
> Columbia, SC 29208
>
> *Please consider the environment before printing this email.*
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at 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.
>

	[[alternative HTML version deleted]]