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,


Frederik

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