[R] How to check if a value of a variable is in a list

From: Frederik Lang <frederiklang_at_gmail.com>
Date: Tue, 19 Apr 2011 23:00:00 -0400

Hi all,

I am working with some social network analysis in R and ran into a problem I just cannot solve.

Each observation in my data consists of a respondent, some characteristics and up to five friends. The problem is that all of these five friends might no show up later as a respondent (observation). Therefore I might not have characteristics on all the friends listed in the data and I want to restrict my data to only those friends that I also have as respondents. The data (without characteristics) look like this:

*resp f1 f2 f3 f4 f5*

ID1           ID5       ID37       ID6        ID2       ID53
ID2           ID1        ID4        ID17      NA        NA

Now, let's say that "ID37" never appears as a respondent, then I want to replace that value with a NA so that it looks like this:

*resp f1 f2 f3 f4 f5*

ID1           ID5        NA        ID6        ID2       ID53
ID2           ID1        ID4        ID17      NA        NA

I thought I could check if for each entry, the value goes again in a list of the respondents.

How do I do this?

Kind regards,


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