Matlab index (I tried to name a matrix to use in a loop like variables.)

I tried to name a matrix to use in a loop like variables.

for example

                 A(1)=[1 2;3 4]

                 A(2)=A(1)*2

                 A(3)=A(2)*2

                    .
                    .

                   .

               A(j)=A(j-1)*2

But I can't use the notation A(j) in the loop. what should I call the j of A?

Answer 1

[bio lim]

You can use cell arrays to do the task. Simple example is,

A{1} = [1 2; 3 4];

 for j = 2 : 10;
    A{j} = A{j-1} * 2;
 end

[Muhammad Usman Saleem]

@coffee do not use braces. It not cell array instead matrix

[bio lim]

It is better to use curly braces rather than using normal brackets. For example, if you define a matrix A, then A(i) suggests the i'th element of the A matrix (as a column vector ). Moreover, your code

n=4; % define accord to your requriements
A(1)=[1 2;3 4]
 for i=1:n
 A(i)=A(i-1)*2;
 end

won't work because in A(i) = B, the number of elements in i and B must be the same.

[Jan]

A{j} is the wanted matrix. The curly braces mean, that the contents of the cell array is replied, not the cell itself.

Answer 2

[Muhammad Usman Saleem]

use the for loop approach to save time. Please define n(representing the times you want these calculations

n=4; % define accord to your requriements
A(1)=[1 2;3 4]
for i=1:n
 A(i)=A(i-1)*2;
end

[Walter Roberson]

No, you are operating upon single elements. The original poster wants to operate on entire matrices.

A(1) = [1 2; 3 4];

is going to give you an error about matrix dimensions not agreeing, as you are attempting to assign a 2 x 2 matrix into a location only large enough to store a scalar.

[Muhammad Usman Saleem]

@Walter actually the given question required little more explanations. Specially in term of output (vector or matrix)

[Walter Roberson]

Either way your code A(1) = [1 2; 3 4]; will not work.

Answer 3

[Jan]

Either use a cell array, as coffee Murun has suggested:

A{1} = [1 2; 3 4];
for j = 2 : 10;
  A{j} = A{j-1} * 2;
end

Or use a 3D-array:

A(:,:,1) = [1 2; 3 4];  % This is the same as: A = [1 2; 3 4]
for j = 2 : 10;
  A(:, :, j) = A(:, :, j-1) * 2;
end