[R] Add blank rows to a dataframe

[David Winsemius]

On Jun 8, 2013, at 4:09 AM, Bert Jacobs wrote:

> Hi,
> 
> I have a vector that looks like this:
> RowSel <-c(0,1,0,1,2,3,0,5,5)
> 
> Now I want to select rows from a specific dataframe DF based on that vector
> like this:
> SubDF <- DF[RowSel,]
> 
> So this works fine, but I was wondering how I could add blank rows add the
> locations in the vector where there is a zero:
> So the final dataframe should look like this:
> 
> SubDF
> [1] blank row
> [2] row 1
> [3] blank row
> [4] row 1 
> [5] row 2
> [6] row 3
> [7] blank row
> [8] row 5
> [9] row 5
> 
> Do I have to use a loop for this or does there exist a straight forward
> function option.

NA's in the selection vector will retrun an NA row, so convert those zeros to NA's :

> str(df)
'data.frame':	9 obs. of  2 variables:
 $ A: num  0 3 9 0 2 0 1 0 1
 $ B: int  1 1 1 2 2 3 3 4 4
> RowSel <-c(0,1,0,1,2,3,0,5,5)
> df[RowSel,]
    A B
1   0 1
1.1 0 1
5   3 1
9   9 1
6   2 2
6.1 2 2
> is.na(RowSel) <- RowSel==0
> df[RowSel,]
      A  B
NA   NA NA
1     0  1
NA.1 NA NA
1.1   0  1
5     3  1
9     9  1
NA.2 NA NA
6     2  2
6.1   2  2

-- 
David Winsemius
Alameda, CA, USA