> Dear R-users,
> I have two dataframes FIRST and SECOND that do not share any rows
> (i.e., there is no unique identifier linking the rows in the two
> dataframes, the rows are independent).
> The dataframes have three variables (in columns) in common, but each
> dataframe also has some variables not shared by the other.
> I wish to merge FIRST and SECOND into a THIRD dataframe, stacking the
> shared columns and including the unshared columns from FIRST and
> SECOND as columns in THIRD. Also, I wish rows in THIRD that do not
> have a value in a particular column (because they came from a
> dataframe without that column) to acquire the value "0" (zero).
> Finally, it it possible to merge >2 dataframes using the
> merge function?
> Any ideas? Thanks, Mark
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