Can I partition a matrix ito several seperated parts ?

can I partition this matrix into 4 parts ?

assume this matrix 29X1, A = [2;2;-3;4;5;6;7;-8;9;-6;5;4;-2;1;3;-9;8;7;4;-5;6;3;2;-1;4;-7;-8;5;-6];

so, I want to group this matrix into 4 seperated groups such as B=7X1, C=7X1, D=7X1, and E=8X1 ?

Answer 1

[Voss]

A = [2;2;-3;4;5;6;7;-8;9;-6;5;4;-2;1;3;-9;8;7;4;-5;6;3;2;-1;4;-7;-8;5;-6];
% maybe this:
B = A(1:7);
C = A(8:14);
D = A(15:21);
E = A(22:29);
% or maybe this:
B = A(2:4:end);
C = A(3:4:end);
D = A(4:4:end);
E = A(1:4:end);
% etc., many other partitionings are possible

[omar th]

first, Thank you for your reply

But, what do you think if the generation of matrix A is related to something random for example, when I ran the code, matrix A is 29x1,,, maybe when I want to run the code for the second time, A matrix will be 35x1,,,so, number of columns is fixed =1, but number of rows can be change.

is there a way to work on that assumption ?

[omar th]

this worked

B = A(2:4:end);

C = A(3:4:end);

D = A(4:4:end);

E = A(1:4:end);

thank you so much

[Walter Roberson]

Ah, I don't think there was any way any of us could have guessed you wanted to select in that order.

[omar th]

actually its not exactly in that order for sure i changed it, but this approach worked in my assumption

thanks again

Answer 2

[Walter Roberson]

A = [2;2;-3;4;5;6;7;-8;9;-6;5;4;-2;1;3;-9;8;7;4;-5;6;3;2;-1;4;-7;-8;5;-6];

parts = mat2cell(A, [7, 7, 7, 8], 1);
[B, C, D, E] = parts{:};

whos

  Name        Size            Bytes  Class     Attributes

  A          29x1               232  double              
  B           7x1                56  double              
  C           7x1                56  double              
  D           7x1                56  double              
  E           8x1                64  double              
  parts       4x1               648  cell                

[omar th]

Thank you for your reply, but as I mentioned above,

what do you think if the generation of matrix A is related to something random for example, when I ran the code, matrix A is 29x1,,, maybe when I want to run the code for the second time, A matrix will be 35x1,,,so, number of columns is fixed =1, but number of rows can be change.

is there a way to work on that assumption ? I mean a way can be adaptive with the given matrix

[Walter Roberson]

Your desired outcome is not defined. Do you always want 4 blocks, and the first three of them should be equal, and the last should absorb any extra capacity ?

A = randi([-9 9], 35, 1);

nrow = size(A,1);
each = floor(nrow/4);
parts = mat2cell(A, [each, each, each, nrow - 3*each], 1);
[B, C, D, E] = parts{:};

whos

  Name        Size            Bytes  Class     Attributes

  A          35x1               280  double              
  B           8x1                64  double              
  C           8x1                64  double              
  D           8x1                64  double              
  E          11x1                88  double              
  each        1x1                 8  double              
  nrow        1x1                 8  double              
  parts       4x1               696  cell                

That gives 8, 8, 8, 11.

But perhaps you would instead prefer 9, 9, 9, 8 -- in which the last matrix might be shorter, but the distribution is more even.

[omar th]

thank you so much