Your data frame didn't come across legibly, try sending it in plain text
using the dput() command.

That said, I'd guess you want something like this:

d[is.na(d$a),"a"] <- d[is.na(d$b),"b"]

The idea is that is.na(d$a) selects only those rows where column "a" is NA
and then moves b values into a for only those rows.

Write back with the dput() data frame if this doesn't work.

Hope this helps,

Michael Weylandt

On Fri, Sep 2, 2011 at 3:51 PM, Josh Tewksbury <tewksjj@uw.edu> wrote:

> Hello, I have a dataframe that looks like this:
>
>  a b  NA Honduras  China NA  NA Sudan  Japan NA  NA Mexico  NA Mexico
> I would like to replace the NA values in column b with the non-NA values in
> column a.  I have tried a number of techniques, (if, ifelse) but I must
> have
> the logic wrong.
>
> Thanks
> --
> Josh
>
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>
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