[R] quoting expressions in a list

[Gabor Grothendieck]

Try this:

> s <- c("df.example$a > 7", "df.example$b < 4")
> sapply(s, function(x) eval(parse(text = x)))
      df.example$a > 7 df.example$b < 4
 [1,]            FALSE             TRUE
 [2,]            FALSE             TRUE
 [3,]            FALSE            FALSE
 [4,]            FALSE            FALSE
 [5,]            FALSE            FALSE
 [6,]            FALSE            FALSE
 [7,]            FALSE             TRUE
 [8,]             TRUE            FALSE
 [9,]             TRUE            FALSE
[10,]             TRUE             TRUE


On Thu, Jul 16, 2009 at 4:44 PM, Erik Iverson<eiverson at nmdp.org> wrote:
> Dear R-help,
>
> I am having quite a difficult time coming up with what I want to do involving named lists.
>
> I have a list of logical expressions, and I would really like it if the "names" of the components of the list were identical to the corresponding logical expression.
>
> So, as an example:
>
> df.example <- data.frame(a = 1:10, b = rnorm(10, 5))
>
> list.example <- list(df.example$a > 7,
>                     df.example$b < 4)
>
> Now what I'd really like is to name the components, and get the results of the following line without having to specify the right-hand side individually for each component:
>
> names(list.example) <- c("df.example$a > 7", "df.example$b < 4")
>
>
> Any ideas?
>
> Best Regards,
> Erik Iverson
>
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