# Define the column and row names.

rownames = c("row1", "row2", "row3", "row4")

colnames = c("col1", "col2", "col3")

​

# Create the matrix.

P <- matrix(c(3:14), nrow = 4, byrow = TRUE, dimnames = list(rownames, colnames))

​

# Access the element at 3rd column and 1st row.

print(P[1,3])

​

# Access the element at 2nd column and 4th row.

print(P[4,2])

​

# Access only the  2nd row.

print(P[2,])

​

# Access only the 3rd column.

print(P[,3])

​