Understand a question. HELP!

Hi guys, can you help me understanding what does the question ask for? Suppose C is the matrix:

             1  2  3 
             4  5  6 
             7  8  9
            10 11 12

Create a matrix C2 that is the upper left 2 × 2 submatrix of C.

Answer 1

[Joseph Cheng]

what submatrix means is a subset formed by taking a block of size mxn (in your example 2x2) from the original matrix. so the 2x2 submatrix of C that is the upper left means it would be the upper left corner 2x2 [1 2;4 5].

So the question is probably asking you to define a new submatrix C2 by the means of array indexing (is that the right word?) instead of hard coding it in. you can read up on it here http://www.mathworks.com/help/matlab/math/matrix-indexing.html. So eventually it would look like:

 C2=C(_somethinghere_).

[AnnaMaria Accardo]

So I should create a new matrix where the upper left is based on C? And the rest of the matrix? How much bigger should C2 be?

[Image Analyst]

C2 will not be bigger. It's the upper left 2x2 of a 4 x 3 matrix, so it's smaller, not bigger. The "rest" of the C matrix is ignored - it's not extracted and put into C2.

[AnnaMaria Accardo]

aaaaah perfect. Thanks Joseph. Easy points for you ;)

[Joseph Cheng]

Anytime, trying to get back into this after a few month hideous.