Accessing Elements of a Matrix.R

#Accessing Elements of a Matrix

# 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, ncol=3, 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])
P[c(1,2),c(1,2)]
P[1:2,1:2]
P['row1','col2']
A <- P[1:2,1:2]
class(A)
B=P['row1','col2']