Sum of an arrays elements

I have an assigntment which sounds like this:

square each element in C and determine the sum of all C's elements

How do i do this? I don't get the right result, that i am supposed to get.

Answer 1

[Mischa Kim]

I'd assume

 C   = [1 2 3];
 res = sum(C.^2)

What is the input, what is the expected result?

[Rasmus]

It does not give me the correct result, as i've already tried that.

[Mischa Kim]

What is the input (vector), what is the expected result?

[Rasmus]

This is the array i have

C =

    10    12    15     4     5     6     0     8     9    10
     7     9    13    14     8    16     0    10     7    20
    31    32    33    34    35    36     0    15    13    40

according to te book, the result should be 1391

[Mischa Kim]

Looking at the numbers, squaring only the last number, 40^2 = 1600, results in a number that is greater than the expected result. So there is a couple of options:

• We don't exactly understand the problem statement.
• The expected result (1391) is incorrect.

[Rasmus]

Yes you are right, and i can now see my mistake. thank you though! :)

[Sagar Damle]

We can see that for given matrix,result can't be 1391.

[Rasmus]

i made a mistake in making the array - so the correct array is this:

C =

    10    12    15     1     1     1     0     1     1     1
     7     9    13     1     1     1     0    10     7     1
     1     1     1     1     1     1     0    15    13     1

But for some reason i dont get the right result. The result is way better then the one before.

I'll just for a safty, write down the assignment, maybe you can se what i am doing wrong.

a) write down the matrix A=[10 12 15; 7 9 13] b)use A to get the transponated matrix. c) write a matrix, C with 4 rows, and 10 columns, all with ones. d)set the element in C's 2 row, 5 column as 8. e) set the whole 7 column in C as 0 f)insert A in C on row 1 and 2 and column 1 to 3, g) insert B in C so C's element in row 2 and column 8 becomes 10. h) remove row 3 in C. i) square each element in C and determine the sum of all C's elements - 1391 is the result.

[Mischa Kim]

A = [10 12 15; 7 9 13];
B = A';
C = ones(4,10);
C(2,5) = 8;
C(:,7) = zeros(4,1);
C(1:2,1:3) = A;
C(2:4,8:9) = B;
C(3,:) = [];

sum(sum(C.^2))
ans =
      1391

[Rasmus]

Hmm weird, that was pretty much what i was doing, but at least now i get the same result.

Thnak you :)

Answer 2

[Sagar Damle]

Rasmus,entered matrix is wrong again! I get this fact from your description. Your matrix is - C =

    10    12    15     1     1     1     0     1     1     1
     7     9    13     1     8     1     0    10     7     1
     1     1     1     1     1     1     0    15    13     1
Any way,I think this is what you want :
A = C.^2; Ans = sum(A(:));
For understanding purpose,see effect of A(:).
Note : For 2-dimentional matrix A, sum(sum(A)) is same as sum(A(:)).
Read help about 'sum()' in MATLAB help.