[R] reshape2's dcast() Adds NAs to Data Frame

[R. Michael Weylandt]

Can you provide a reproducible example? See, e.g.,

http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example

for information on how to do so.

My entirely unjustified guess is that the NAs appear for combinations
of factor levels that don't exist.

Michael

On Tue, Aug 7, 2012 at 4:45 PM, Rich Shepard <rshepard at appl-ecosys.com> wrote:
>   I need to understand how and why dcast() adds NAs to a data frame that
> contained no missing values.
>
>   The database table of chemical concentrations has all missing values
> removed because they cannot contribute to data analyses. The structure of
> the R data frame of these data have no NA values, and neither does the data
> frame resulting from applying the reshape2 melt() function to it. However,
> the data frame produced by the dcast() function does contain NAs for all
> chemicals. I assume this is because of the syntax I used:
>
> chem.cast <- dcast(chem.melt, site + sampdate + era + ceneq1 + floor +
> ceiling ~ param)
>
>   How should I reshape the data frame from long to wide without adding these
> spurious NAs?
>
> Rich
>
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