[R] creating a new column with values from another

[Patrick Connolly]

On Mon, 12-Sep-2011 at 12:35PM -0700, holly shakya wrote:

|> I have 2 columns for weight. There are NAs in each column but not for the
|> same observation. Some observations have values for both.  I would want to
|> prioritize the WT2 values so I would like to do the following:
|> 
|> >From this:
|> ID          WT1    WT2
|> 1           134      NA
|> 2           145       155
|> 1            NA      175
|> 3            NA      187
|> 
|> To this:
|> ID    WT1       WT2    WT
|> 1        NA         175     175
|> 2      145         155      155
|> 3       NA         187      187
|> 
|> Populating the NA values of wt2 with those of wt1 would work as well. Any
|> suggestions would be greatly appreciated.

If xx is your dataframe, and the NAs are as you describe, this will
get you close to what you want.

> xx <- within(xx, WT <- WT2)
> xx <- within(xx, WT[is.na(WT2)] <- WT1[is.na(WT2)])
> aggregate(WT ~ ID, function(x) max(x), data = xx)

  ID  WT
1  1 175
2  2 155
3  3 187


You're almost there.




|> -- 
|> Holly Shakya
|> 
|> Doctoral Student
|> San Diego State University/University of California, San Diego
|> Joint Doctoral Program in Public Health
|> (Global Health)
|> 
|> 	[[alternative HTML version deleted]]
|> 
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|> and provide commented, minimal, self-contained, reproducible code.

-- 
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   ___    Patrick Connolly   
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