Change dimension of a matrix

You cannot because the number of elements will change. 131072 is not equal to 256^2 so what are you going to do with all the left over elements? You can choose a subset of the 131,072 elements in your vector to create a 256x256 matrix.

x = randn(131072,1);
y = x(1:65536);
y = reshape(y,256,256);

You can reshape it to 256x512, or 512x256 using reshape.

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Answer 3

Image Analyst 2012-9-14

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You can change the number of elements if you want. If you have the Image Processing Toolbox, you can use imresize()

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Answer 4

Ilayat Ali 2023-9-13

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You can change the dimensions of a matrix using various functions and techniques, depending on your specific requirements. Here are some common ways to modify the dimensions of a matrix:

1. Reshaping a Matrix: You can change the dimensions of a matrix without changing its data by using the reshape function. This function rearranges the elements of the matrix while preserving their values. Here's how to use it:

A = [1, 2, 3; 4, 5, 6];

B = reshape(A, 3, 2); % Reshape A into a 3x2 matrix

2. Transposing a Matrix: You can change the dimensions of a matrix by transposing it. This swaps the rows and columns. Use the ' operator for matrix transpose:

A = [1, 2, 3; 4, 5, 6];

B = A'; % Transpose A, changing it from a 2x3 matrix to a 3x2 matrix

3. Slicing: You can extract submatrices from a larger matrix to change its dimensions. For example, to extract a specific subset of rows and columns:

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

B = A(1:2, 1:2); % Extract a 2x2 submatrix from A

4. Concatenation: You can concatenate matrices to change their dimensions. For example, to horizontally concatenate two matrices:

A = [1, 2; 3, 4];

B = [5, 6; 7, 8];

C = [A, B]; % Concatenate A and B horizontally, resulting in a 2x4 matrix

5. Resizing: You can change the size of a matrix using functions like zeros, ones, or rand. For example, to change a matrix A to a larger size while keeping its data:

A = [1, 2; 3, 4];

newSize = [3, 3]; % New size

B = zeros(newSize); % Create a new matrix with zeros

B(1:size(A, 1), 1:size(A, 2)) = A; % Copy the data from A to B

These are some common techniques for changing the dimensions of a matrix in MATLAB. The method you choose depends on your specific data manipulation needs.