How to delete specific rows and columns from a matrix in a smarter way?

Question

Let\'s say t1 is :

t1 <- array(1:20, dim=c(10,10))

      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
 [1,]    1   11    1   11    1   11          


        

Answer 1

You can do:

t1<- t1[-4:-6,-7:-9]