# [R] Inserting a new row in a matrix

Alex99 loyola9988 at yahoo.com
Tue Oct 21 20:19:31 CEST 2008

```Hi guys,

I need to insert a row to a matrix in a for loop. I have matrix named "Avg"
which is a 5x4 matrix of zeros.
I have a file named "A"(4 rows,14 columns) which I make a sample of it 5
times. each time I get the mean for each column and put the result in the
"Avg" matrix. this is my code:

Avg=matrix(0,5,4)
>
>  for(i in 1:5){
+  res=(A[sample(nrow(A), 5),])
+  insertRow(Avg,i,colMeans(res))
+  show(res)
+  show(Avg)
+  }

this is my result(I just copied the first sample) :

s1 s2 s3 s4
2    1  0  1  0
3    0  0  0  0
11  0  0  0  0
5    0  1  0  1
12  0  0  0  0
[,1] [,2] [,3] [,4]
[1,]    0    0    0    0
[2,]    0    0    0    0
[3,]    0    0    0    0
[4,]    0    0    0    0
[5,]    0    0    0    0

it's suppose to put .2 .2 .2 .2 in the first row of the matrix but as you
see it's all 0. any idea why and how to fix it?

Thanks,

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```