[R] How can I get "A$Title"?

Prof Brian D Ripley ripley at stats.ox.ac.uk
Mon Dec 18 09:11:33 CET 2000

On Mon, 18 Dec 2000, C. Joseph Lu wrote:

> Dear R-friends,
> I have whole bunch of objects, say, A, B, ..., Z,
> all of them are "list" and haveing "Title" (a character string)
> as their first element.
> E.g.,
>   > A$Title
>   [1] "Airplane Component"
> What I like to do is to find a way to printout all the Titles at one
> time.
> I tried the following:
>   >  paste(LETTERS, "Title", sep="$") -> tmp
> but can't find a way to continue since
>   > get(tmp[1])
>   Error in get(x, envir, mode, inherits) : variable "A$Title" was not
> found

Right: the variable is named A, not A$Title.

> Is there a way to create a vector of A$Title, B$Title, ... without
> double quotes?

Do you want the names or the values?  For the latter

sapply(as.list(LETTERS), function(x) get(x[1])$Title)

The quotes are part of the printing of the titles, not the titles
themselves: use cat() or print(quote=FALSE) to suppress them.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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