# [R] Deleting rows satisfying a certain condition (sum of some colums>2)

From: Katie C <katie.cheon_at_gmail.com>
Date: Fri, 07 Mar 2008 21:17:35 -0800 (PST)

I have a huge matrix and need to delete certain rows. What I need to do is: 1.In each row, calculate the sum of jth column and (J+2)th column 2. If the sum is greater than 2 then that row needs to be deleted.

I have a sample matrix and my codes here. It does remove some rows but when it does, it skips the next row and each time it deletes a row, the dimension changes so it gets out of bound. I tried to fix those problems but it did not work. Any suggestions please? Thank you.

S1=c(2,2,2,2,2,2,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,2,2, 1,1,1,1,1,1,2,1,1,0,0,0,2,1,1,0,0,0,2,1,1,0,0,0,2,2,1,2,1,0,2,2,1,2,1,0,2,2,1,2,1,0);

SS=matrix(S1,nrow=18);

for (i in 1:nr){

for (j in 1:nc){

```        #print(paste("Sum=",SS[i,j]+SS[i,j+nt],"  ms=",ms));
if (SS[i,j]+SS[i,j+nt]> ms){
SS=SS[-i,]
nr=dim(SS)[1] #this doesn't update nr in the outer for loop. why?
print(nr) }
```

}
# i=i-1 #this doesn't help to avoid skipping rows }
SS;
```--
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