[R] Reducing a matrix

[Dimitris Rizopoulos]

if you don't mind having zeros instead of NAs, then yet another solution is:

df <- read.table(textConnection("x y1 y2 y3 y4
1   3  7 NA NA NA
2   3 NA 16 NA NA
3   3 NA NA 12 NA
4   3 NA NA NA 18
5   6  8 NA NA NA
6  10 NA NA  2 NA
7  10 NA 11 NA NA
8  14 NA NA NA  8
9  14 NA  9 NA NA
10 15 NA NA NA 11
11 50 NA NA 13 NA
12 50 20 NA NA NA"), header = TRUE)
closeAllConnections()

out <- rowsum(df[-1], df$x, na.rm = TRUE)
out$x <- as.numeric(row.names(out))
out


I hope it helps.

Best,
Dimitris


On 2/28/2010 1:56 AM, Juliet Ndukum wrote:
> I wish to rearrange the matrix, df, such that all there are not repeated x values. Particularly, for each value of x that is reated, the corresponded y value should fall under the appropriate column.  For example, the x value 3 appears 4 times under the different columns of y, i.e. y1,y2,y3,y4. The output should be such that for the lone value of 3 selected for x, the corresponding row entries with be 7 under column y1, 16 under column y2, 12 under column y3 and 18 under column y4. This should work for  the other rows of x with repeated values.
> df
>     x y1 y2 y3 y4
> 1   3  7 NA NA NA
> 2   3 NA 16 NA NA
> 3   3 NA NA 12 NA
> 4   3 NA NA NA 18
> 5   6  8 NA NA NA
> 6  10 NA NA  2 NA
> 7  10 NA 11 NA NA
> 8  14 NA NA NA  8
> 9  14 NA  9 NA NA
> 10 15 NA NA NA 11
> 11 50 NA NA 13 NA
> 12 50 20 NA NA NA
>
> The output should be:
>
>     x y1 y2 y3 y4
> 1   3  7 16 12 18
> 2   6  8 NA NA NA
> 3  10 NA 11  2 NA
> 4  14 NA 9 NA  8
> 5 15 NA NA NA 11
> 6 50 20 NA 13 NA
>
> Can any write for me a code that would produce these results.
> Thank you in advance for your help.
>
> JN
>
>
>
> 	[[alternative HTML version deleted]]
>
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-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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