Shall I extract data from Matrix by group seperately?

Now I have a matrix as below:

z =

    1.0000   -7.6365
    2.0000    1.7736
    3.0000  -11.1412
    4.0000  -10.1350
    5.0000    0.9315
    1.0000   16.3263
    2.0000   -6.6967
    3.0000    4.7138
    4.0000   -1.2558
    5.0000   12.1736
    1.0000    6.4000
    2.0000    4.5000
    3.0000    3.5000
I can use function-'sort' to deal with it as below:

 sortrows(z)

ans =

    1.0000   -7.6365
    1.0000    6.4000
    1.0000   16.3263
    2.0000   -6.6967
    2.0000    1.7736
    2.0000    4.5000
    3.0000  -11.1412
    3.0000    3.5000
    3.0000    4.7138
    4.0000  -10.1350
    4.0000   -1.2558
    5.0000    0.9315
    5.0000   12.1736

Now I want to get the data like below:

n1=

-7.6365
 6.4000
 16.3263

n2=

-6.6967
 1.7736
 4.5000

n3=

 -11.1412
   3.5000
   4.7138

n4=

 -10.1350
 -1.2558

n5=

0.9315
12.1736

How shall I get n1,n2,n3,n4,n5 better and what if I want to get n1,n2,...n100?

[the cyclist]

When you do the sort, do you really want to sort each columns independently, or did you mean to keep rows intact? If the latter, you want to use the sortrows command.

[vx2008]

yes, just as you guess; Thanks for your reminding.

[Stephen23]

"How shall I get n1,n2,n3,n4,n5 better and what if I want to get n1,n2,...n100?"

Don't

You really don't want to do this. It is poor way to program and will make your programming buggy, slow and complicated. If you want to know why, then read about it here:

http://www.mathworks.com/matlabcentral/answers/196952-how-to-create-new-variables-in-batches-with-strcat

http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F

Answer 1

[the cyclist]

Here's one way:

z= [1.0000   -7.6365
    2.0000    1.7736
    3.0000  -11.1412
    4.0000  -10.1350
    5.0000    0.9315
    1.0000   16.3263
    2.0000   -6.6967
    3.0000    4.7138
    4.0000   -1.2558
    5.0000   12.1736
    1.0000    6.4000
    2.0000    4.5000
    3.0000    3.5000];

sorted_z = sortrows(z,[1 2]);

[uz, ~, j] = unique(sorted_z(:,1));

numberUnique = numel(uz);

n = cell(numberUnique,1);

for nu = 1:numberUnique
    indexToThisValue = (j==nu);
    n{nu} = sorted_z(indexToThisValue,2);
end

Your vectors are stored in the elements of the cell array: n{1}, n{2}, etc.

This is much better than storing them in individual variables n1, n2, etc. You can read about that in many threads in this forum.