R help - Mar 2010 - using a condition given as string in subset function - how?

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I know that if you have to resort to 'parse(text=...)', you should look
for
another way (it is a 'fortune'), but it is getting late, and at least it
works:
> eval(parse(text="subset(df, A==1 & B==1)"))
  A B
1 1 1


On Sat, Mar 20, 2010 at 9:09 PM, Mark Heckmann <mark.heckmann@gmx.de>
wrote:
> df <- data.frame(A=c(1,2), B=c(1,1))
>
> I have a string containing a condition for a subset function, like:
> conditionAsString <- paste(names(df), df[1,], sep="==",
collapse=" & ")
>  > conditionAsString
>  > "A==1 & B==1"
>
> Now I want to use this string in the subset call, like
>
> subset(df, conditionAsString)
>
> I do not exactly now how to combine substitute, expression, parse and
> so on to get what I want, which would be:
>
> subset(df, A==1 & B==1)
>
> but using the string conditionAsString.
>
> Thanks,
> Mark
> –––––––––––––––––––––––––––––––––––––––
> Mark Heckmann
> Blog: www.markheckmann.de
> R-Blog: http://ryouready.wordpress.com
>
>
>
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

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