How to get a random 50x14 matrix from 300x14 matrix

Hello,

Could you please tell me how to get a random 50x14 matrix from 300x14 matrix?

[Scott MacKenzie]

It's not clear what you are trying to do. Do you simply want to pick 50 rows at random from the 300 rows in the matrix? If you are trying to do something else, please explain.

[Amirali AGHAMIRI]

No, I have a 300x14 matrix, and I want to generate a random matrix with the size of 50x14 from it.

Thank you in advance.

[Scott MacKenzie]

@Amirali AGHAMIRI, @Torsten has posted an answer. Perhaps that is what you are after

[Amirali AGHAMIRI]

Thanks.

Answer 1

[Image Analyst]

Perhaps this, if you want all 50 rows to be adjacent to each other and not randomly chosen.

% Define matrix.
m = randi(9, 300, 14)
% Get starting and ending rows
startingRow = randi(size(m, 1)-49, 1, 1)
endingRow = startingRow + 49
% Extract a band of 50 contiguous rows
m50 = m(startingRow : endingRow, :);

[Amirali AGHAMIRI]

Thank you for your answer. But for my case the 300x14 matrix is already defined( I have specific values for them, so it's not random), and I want to generate a 50x14 matrix (that 50 rows to be adjacent to each other) out of it . Do you have any idea?

[Image Analyst]

So just delete the first line where I created an m. I just did that because you keep forgetting to attach your actual matrix in a .mat file with the paperclip icon.

% Get starting and ending rows
startingRow = randi(300-49, 1, 1)

startingRow = 207

endingRow = startingRow + 49

endingRow = 256

As you can see above when I ran it, it would take all rows between 207 and 256 of your original matrix and extract them to a new matrix called m50. Why do you think that will not work for your matrix?

[Amirali AGHAMIRI]

Thanks, it works.

Answer 2

[Torsten]

A = rand(300,14);
p = randperm(300,50);
B = A(p,:)

[Amirali AGHAMIRI]

Thanks.