How to convert cell to matrix

hi

How to convert cell to matrix in this situation

t= readtable('loopTest');

for i=1:3
    new_matrix{i}=t(:,i*3);
end

new_matrix=cell2mat(new_matrix) % this is not work:(
new_matrix=mean(new_matrix)

It is important for me to use the readtable function and not readmatrix

If I did this in the readmatrix function I would get a matrix of 16 * 3

This is what I want only with function"readtable"

Answer 1

[Walter Roberson]

    new_matrix{i}=t{:,i*3};

[Shahar ben ezra]

TNX!