The following exercises are meant to be answered by few lines of MATLAB code; mo

Question

The following exercises are meant to be answered by few lines of MATLAB code; most of them could be expressed in a single line of code or command. The command may be involved (i.e., it may use a number of parentheses or calls to functions) but can, in essence, be solved by the execution of a single command. If the problem is too complicated, feel free to break it up over two or more lines and later to collapse it into a single line.

4. Given the array A = [2 7 9 7 ; 3 1 5 6 ; 8 1 2 5], explain the results of the following commands:

a. A'

b. A(:,[1 4])

c. A([2 3],[3 1])

d. reshape(A,2,6)

e. A(:)

f. flipud(A)

g. fliplr(A)

h. [A A(end,:)]

i. A(1:3,:)

j. [A ; A(1:2,:)]

k. sum(A)

l. sum(A')

m. sum(A,2)

n. [ [ A ; sum(A) ] [ sum(A,2) ; sum(A(:)) ] ]

Explanation / Answer

>> A'

ans =

2 3 8
7 1 1
9 5 2
7 6 5

>> A(:,[1 4])

ans =

2 7
3 6
8 5

>> A([2 3],[3 1])

ans =

5 3
2 8

>> reshape(A,2,6)

ans =

2 8 1 9 2 6
3 7 1 5 7 5

>> A(:)

ans =

2
3
8
7
1
1
9
5
2
7
6
5

>> flipud(A)

ans =

8 1 2 5
3 1 5 6
2 7 9 7

fliplr(A)

ans =

7 9 7 2
6 5 1 3
5 2 1 8

>> A(1:3,:)

ans =

2 7 9 7
3 1 5 6
8 1 2 5

[A ; A(1:2,:)]

ans =

2 7 9 7
3 1 5 6
8 1 2 5
2 7 9 7
3 1 5 6

>> sum(A)

ans =

13 9 16 18

>> sum(A')

ans =

25 15 16

>> sum(A,2)

ans =

25
15
16

>> [ [ A ; sum(A) ] [ sum(A,2) ; sum(A(:)) ] ]

ans =

2 7 9 7 25
3 1 5 6 15
8 1 2 5 16
13 9 16 18 56

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