Managing Matrix Content Using Loop ?

e.g i have variable data that containt matrix like these ;

a1 b1 c1

a2 b2 c2

a3 b3 c3

and i wanted it stored like :

a1

a2

a3

b1

b2

b3

c1

c2

c3

I use looping

    inc=1;
    [s1,s2]=size(data);
    for x=1:s2
        for y=1:s1
        dataStored(inc)=data(y,x);
        inc=inc+1;
        end
    end

It's work, but on a very large amount of data like data < 512x3671 int 16 > take endless time to wait. Is there any way simple to do that? Or maybe my code is wrong ?

Answer 1

[Cedric]

 >> A = magic(3)           % Just an example..
 A =
     8     1     6
     3     5     7
     4     9     2

 >> v = A(:)               % Read A as a column vector (linear indexing).
 v =
     8
     3
     4
     1
     5
     9
     6
     7
     2

[I Made]

Thanks, it can be simple like that. It's really sweet, can you give me link to do trick-trick in matlab ? if i have 2 variable in matrix, eg i have a

a1

a2

a3

and variable b

b1

b2

b3

i wanted to store it in c like

a1 b1

a2 b2

a3 b3

i need some tutorial to get over with matrix management issue.. really

[Cedric]

Google "MATLAB tutorial" or pick one here:

http://www.mathworks.com/academia/student_center/tutorials/launchpad.html

e.g. the Getting Started 2MB PDF.

What we are using in my solution is linear indexing. There aren't that many types of indexing: subscribed, linear, logical.

For your second question, you want to read the doc about CAT, HORZCAT, VERTCAT. You can also do it this way:

 a = [6, 7, 8].'
 b = [1, 2, 3].' 
 c = [a,b]

This outputs

 a =
     6
     7
     8

 b =
     1
     2
     3

 c =
     6     1
     7     2
     8     3

[I Made]

How if b variable is less than a variable like

a1

a2

a3

but then b only

b1

b2

this will make Subscripted assignment dimension mismatch. How do i put it like

a1 b1

a2 b2

a3 0

[Cedric]

You can only CAT arrays on dimensions with same length. If you are not in this situation, you have fist to adapt lengths. If b had been a 2x1 vector in the previous case, I would have had to add some padding, e.g. 0, to match lengths:

 >> [a, [b;0]]
 ans =
     6     1
     7     2
     8     0

[I Made]

i tried it but get another error : CAT arguments dimensions are not consistent...

which my variable : a < 1879552x1 int16 > and b < 1879402x1 int16 > then i do :

c = [a, [b;0]]

[Cedric]

Well, [b;0] adds only one 0 element to b and look at the size of each of your vectors.. the size difference is much greater than just one element. It is 150 actually. Now if it is really meaningful to add 150 0's to b, you can do it as follows:

 bext = [b; zeros(150,1)] ;
 c = [a, bext] ;

but as far as I'm concerned, it would be a good investment of your time to read a tutorial, so you understand at least the basics about array manipulation in MATLAB.