How can I add a column with labelining in a matrix

I have data matrix. I have to add label column with same name Before in the matrix. How I can add this labeling?

Answer 1

[Chunru]

% Create a table with some data
a = (1:10)'; b=rand(10, 1); c=randi([1,100], 10, 1);
T = table(a, b, c)

T = 10×3 table
    a        b       c 
    __    _______    __

     1    0.31924    57
     2    0.41572     9
     3    0.33329    31
     4    0.52433    42
     5    0.60832     6
     6    0.56471     1
     7    0.19825    51
     8    0.20861    67
     9    0.75822    19
    10     0.8956    96

% Now add the label
T.label = repmat("Before", 10, 1);
T = T(:, [end 1:end-1])

T = 10×4 table
     label      a        b       c 
    ________    __    _______    __

    "Before"     1    0.31924    57
    "Before"     2    0.41572     9
    "Before"     3    0.33329    31
    "Before"     4    0.52433    42
    "Before"     5    0.60832     6
    "Before"     6    0.56471     1
    "Before"     7    0.19825    51
    "Before"     8    0.20861    67
    "Before"     9    0.75822    19
    "Before"    10     0.8956    96

[Sazid Hasan]

Thank you very much. If I split label like before and after 5 for before and 5 for after how it will be done? As i try define the size, it not working.