conditional replacement of character strings in vectors

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.

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 at 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