Is it true that this is a vector?
matrix(1)
No,
because matrix(1) is two-dimensional.
Is it true that this is a vector?
[,1] [1,] 1
No,
because this is the result of matrix(1) and matrix(1) is two-dimensional.
How many dimensions does m have when m is
matrix(1,1)
two
because m is a matrix.
How many dimensions does m have when m is
matrix(1,2)
two
because m is a matrix.
How many dimensions does m have when m is
matrix(1,2,3)
two
because m is a matrix.
How many rows does m have when m is
matrix(1,2,3)
two
because the second argument in m is 2.
How many columns does m have when m is
matrix(1,2,3)
three
because the third argument in m is 3.
What is dim(m) when m is
matrix(1,2,3)
2 3
because dim() is the same as asking the values of the dimensions of a matrix.
How many values does m have when m is
matrix(1,2,3)
six
because two rows times three columns is six.
What is sum(m) where m is
matrix(1,2,3)
six
because there are six values in m and each value is equal to one.
What is sum(m) where m is
matrix(2,2,3)
twelve
because there are six values in m and each value is equal to two.
What is length(m) where m is
matrix(2,2,3)
six
because there are six values in m.
How many columns does m have where m is
matrix(15,1,15)
and
dim(m) <- c(3,5)
5
because m was altered to have five columns by dim.
How many columns does m have where m is
matrix(20,4,5)
and
dim(m) <- c(2,20)
5
because the m is 20, but the number of values produced by dim(m) <- c(2,20) is 40.
What is m[1,3] where m is
matrix(c(1,2,3),3,3)
1
because matrix(c(1,2,3),3,3) is
[,1] [,2] [,3] [1,] 1 1 1 [2,] 2 2 2 [3,] 3 3 3
and the value in the first row, third column is 1.
What is m[1,3] where m is
matrix(c(1,2,3),2,3)
2
because matrix(c(1,2,3),2,3) is
[,1] [,2] [,3] [1,] 1 3 2 [2,] 2 1 3
and the value in the first row, third column is 2.
What is the name of the second column of m when m is
matrix(c(1,2,3),3,3)
and
colnames(m) <- c("April", "May", "June")
"May"
because "May" is the second value given to colnames.
What is m[1,3] where m is
matrix(1:6,2,3)
5
because matrix(1:6,2,3) is
[,1] [,2] [,3] [1,] 1 3 5 [2,] 2 4 6
and the value in the first row, third column is 5.
What is m[1,3] where m is
matrix(1:6,3,3)
1
because matrix(1:6,3,3) is
[,1] [,2] [,3] [1,] 1 4 1 [2,] 2 5 2 [3,] 3 6 3
and the value in the first row, third column is 1.
What is m[1,2] where m is
c(1,2,3,4)
and
dim(m) <- c(2,2)
3
because m is now
[,1] [,2] [1,] 1 3 [2,] 2 4
and the value in the first row, second column is 3.
What is class(m[1,2]) where m is
c(1,2,3,4)
and
dim(m) <- c(2,2)
integer
because the matrix was made out of an integer vector.
What is m[2,2] where m is
list(1,"2",3,"4")
and
dim(m) <- c(2,2)
[[1]] [1] "4"
because m is now
[,1] [,2] [1,] 1 3 [2,] "2" "4"
What is class(m[2,2]) where m is
list(1,"2",3,"4")
and
dim(m) <- c(2,2)
list
because the matrix was made out of a list.