[R] Creating binary variable depending on strings of two dataframes

[Gabor Grothendieck]

On Tue, Dec 7, 2010 at 11:30 AM, Pete Pete <noxyport at gmail.com> wrote:
>
> Hi,
> consider the following two dataframes:
> x1=c("232","3454","3455","342","13")
> x2=c("1","1","1","0","0")
> data1=data.frame(x1,x2)
>
> y1=c("232","232","3454","3454","3455","342","13","13","13","13")
> y2=c("E1","F3","F5","E1","E2","H4","F8","G3","E1","H2")
> data2=data.frame(y1,y2)
>
> I need a new column in dataframe data1 (x3), which is either 0 or 1
> depending if the value "E1" in y2 of data2 is true while x1=y1. The result
> of data1 should look like this:
>   x1     x2 x3
> 1 232   1   1
> 2 3454 1   1
> 3 3455 1   0
> 4 342   0   0
> 5 13     0   1
>
> I think a SQL command could help me but I am too inexperienced with it to
> get there.
>

Try this:

> library(sqldf)
> sqldf("select x1, x2, max(y2 = 'E1') x3 from data1 d1 left join data2 d2 on (x1 = y1) group by x1, x2 order by d1.rowid")
    x1 x2 x3
1  232  1  1
2 3454  1  1
3 3455  1  0
4  342  0  0
5   13  0  1


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