If and only if the matrices have the same number of columns, you can concatenate two matrices vertically using,
M = [m1; m2]; % where m1 and m2 are matrices with the same number of columns.
To add a new row,
M(end+1,:) = NaN; % or 0, or any other scalar value.
Another solution would be to save the matrices within a cell array and concatenate them later, after the loop; again, equal column numbers are required.
C = cell(n,1);
for i = 1:n
C{i} = mat; % mat is a matrix
end
M = vertcat(C{:});
Once the matrix is complete, the plot() function will plot one line object per column
plot(M, '-')
