I need to add to this matrix a row of `0`

(zeros) above and a column of `0`

on the left.

I tried to do it like this ...

```
R <- rbind(Hxx, 0)
R <- cbind(R, 0)
```

... but I add the row and column at the end. When I had them in the end, I tried with `R[,(1,8)]<- R[,(8,1)]`

, but it did not work.

How to solve this?