How to create vector which is linear combination of a matrix

Hi,

I have my matrix M as:

M = [1,2,3; 4,5,6; 7,8,9];

I am trying to create a vector that is a linear combination of the columns of M. I am doing it this way:

vec= [2*M(:,1); 3*M(:,2); 4*M(:,3)];

Its resulting in:

vec =

2

8

14

6

15

24

12

24

36

It doesn't seem right to me. Can you please help me in that? Any help will be really appreciated. Thanks in advance.

[Karim]

You will need to expand a bit on why it doesn't seem right ... what would you expect as output?

[aliza mustafa]

I was making mistake in making the vector. I got it done this way:

vec= 2*M(:,1) + 3*M(:,2) + 4*M(:,3);

Thanks :)

Answer 1

[Matt J]

Perhaps you instead meant to have,

M = [1,2,3; 4,5,6; 7,8,9];

vec=M*[2;3;4]

vec = 3×1

20 47 74

[aliza mustafa]

Thanks for helping :)

Answer 2

[Chunru]

M = [1,2,3; 4,5,6; 7,8,9]

M = 3×3

1 2 3 4 5 6 7 8 9

vec= sum([2*M(:,1) 3*M(:,2) 4*M(:,3)], 2)

vec = 3×1

20 47 74

% Alternatively
vec =M*[2; 3; 4]

vec = 3×1

20 47 74

[aliza mustafa]

Thanks for helping :)