How to split the last 4 elements in a column into a new column?

If I have a column, say

5

7

2

3

6

4

9

and I want to split the first 3 elements and the last 4 elements into 2 column, like this,

5 3

7 6

2 4

9

Could anyone please tell me how I can do this? I thought about using reshape, but since my first column and second column do not have the same number of elements, reshape seems not applicable.

Answer 1

[Voss]

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

M = 7×1

5 7 2 3 6 4 9

You can't use a matrix, like you said, because the lengths of the two new column vectors is not the same.

You could use a cell array:

C = {M(1:3) M(4:end)}

C = 1×2 cell array
    {3×1 double}    {4×1 double}

C{:} % show the contents of C

ans = 3×1

5 7 2

ans = 4×1

3 6 4 9

Or you can make two new variables, where each is a column vector:

M1 = M(1:3)

M1 = 3×1

5 7 2

M2 = M(4:end)

M2 = 4×1

3 6 4 9

[Julia]

Thank you so much! Why didn't I think about dividing them into new variables...

[Voss]

You're welcome!

Answer 2

[Les Beckham]

I'm not sure why you want to do this, or what you intend to do with the results, but here is one possible way using a cell array.

A = [ ...
5
7
2
3
6
4
9];
B = {A(1:3), A(4:end)}

B = 1×2 cell array
    {3×1 double}    {4×1 double}

B{1}

ans = 3×1

5 7 2

B{2}

ans = 4×1

3 6 4 9

Answer 3

[Constantino Carlos Reyes-Aldasoro]

In Matlab is better to think of matrices than to think of columns (like you would do in Excel for instance), so think of your first column as a matrix

a= [5 7 2 3 6 4 9]'

a = 7×1

5 7 2 3 6 4 9

Then, if you want to "move" elements of that matrix (before you decide where) you need to use the address of those elements, e.g.

a(end-3:end)

ans = 4×1

3 6 4 9

That took the last four elements of the matrix. Now, where to move them, you can paste them into the second column of a, but the dimensions would not match directly, and also, you would need to remove those elements, which you only have selected, so better try a new matrix, and do one step at a time:

b(1:3,1) = a(1:3)

b = 3×1

5 7 2

b(1:4,2) = a(end-3:end)

b = 4×2

5 3 7 6 2 4 0 9

Notice that a zero was appended at the end of the first column. It would be same if you start adding elements beyond the existing ones, Matlab will complete the matrix, e.g.

b(6,4) = 11

b = 6×4

5 3 0 0 7 6 0 0 2 4 0 0 0 9 0 0 0 0 0 0 0 0 0 11

So, this would be a way to to split the last 4 elements in a column into a new column.