Hi Joris,

Thanks very much. I think the %in% ls() was the key. I just needed to know
how to select elements that existed  in ls().

Scott

On Sat, Jun 5, 2010 at 4:22 PM, Joris Meys <jorismeys@gmail.com> wrote:

> Hi,
>
> One possible way to get around it is using following idea :
> X1 <- rnorm(10)
> X2 <- rnorm(10)
>
> Names <- c("X1","X2","X3")
> Names <- Names[Names %in% ls()]
>
> n <- length(Names)
> p <- 10   #length of each object
> output <- matrix(NA,ncol=n,nrow=p)
>
> for(i in 1:n){
>    output[,i] <- get(Names[i])
> }
> output <- as.data.frame(output)
> names(output) <- Names
>
> You can also use an eval-parse construct like this :
> ## Alternative
> Names <- c("X1","X2","X3")
> Names <- Names[Names %in% ls()]
> Names <- paste(Names,collapse=",")
> expr = paste("output <- data.frame(",Names,")",sep="")
> eval(parse(text=expr))
>
> Both are not really the most optimal solution, but do work. It would
> be better if you made a list or matrix beforehand and then save the
> results of the calculations in that list or matrix whenever the
> calculation turns out to give a result.
>
> Cheers
> Joris
>
> On Sat, Jun 5, 2010 at 1:23 AM, Scott Chamberlain <schamber@rice.edu>
> wrote:
> > Hello, I am trying to make a data frame from many elements after
> > running a function which creates many elements, some of which may not
> > end up being real elements due to errors or missing data. For example,
> > I have the following three elements p1s, p2s, and p3s. p9s did not
> > generate the same data as there was an error in the function for some
> > reason. I currently have to delete p9s from the data.frame() command
> > to get the data.frame to work.  How can I make a data frame by somehow
> > ignoring elements (e.g., p9s) that do not exist, without having to
> > delete each missing element from data.frame()? The below is an example
> > of the code.
> >
> >> p1s
> >      statistic parameter p.value
> > [1,] 3.606518  153       0.0004195377
> >> p2s
> >      statistic parameter p.value
> > [1,] -3.412436 8         0.009190015
> >> p3s
> >      statistic parameter p.value
> > [1,] 1.543685  599       0.1231928
> >
> >> t(data.frame(t(p1s),t(p2s),t(p3s),t(p9s)))
> > Error in t(p9s) : object 'p9s' not found
> >
> >
> > Thanks, Scott Chamberlain
> > Rice University
> > Houston, TX
> >
> > ______________________________________________
> > 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.
> >
>
>
>
> --
> Ghent University
> Faculty of Bioscience Engineering
> Department of Applied mathematics, biometrics and process control
>
> tel : +32 9 264 59 87
> Joris.Meys@Ugent.be
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