You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: CBIG_uniform_rand_rotation.m
    path of file: ./repos/CBIG/utilities/matlab/stats
    
    the code of the file until where you have to start completion: function M = CBIG_uniform_rand_rotation(num_rotations, seed)

% M = CBIG_uniform_rand_rotation(num_rotations, seed)
%
% This function is used to compute a uniformly distributed rotation matrix
% (UDRM). To compute the UDRM, and from a macro/big-picture view, the
% function performs the fast random rotation matrix method. This involves
% generating the householder matrix H, and the simple rotation matrix R to
% compute M, the UDRM.
%
% INPUT:
%       - num_rotations
%         A scalar value used to indicate the desired number of rotations.

    
function M = CBIG_uniform_rand_rotation(num_rotations, seed)

% M = CBIG_uniform_rand_rotation(num_rotations, seed)
%
% This function is used to compute a uniformly distributed rotation matrix
% (UDRM). To compute the UDRM, and from a macro/big-picture view, the
% function performs the fast random rotation matrix method. This involves
% generating the householder matrix H, and the simple rotation matrix R to
% compute M, the UDRM.
%
% INPUT:
%       - num_rotations
%         A scalar value used to indicate the desired number of rotations.
%         The default value is 1000.
%
%       - seed
%         A scalar value used to define the random seed for the purpose of
%         producing random rotation.
%         The default value is 1.
%
% OUTPUT:
%       - M:
%         A 3x3xnum_rotations matrix, the UDRM for each rotation
%
% Example:
% num_rotations = 5000;
% seed = 2;
% M = CBIG_uniform_rand_rotation(num_rotations, seed);
%Written by Ruby Kong and CBIG under MIT license: https://github.com/ThomasYeoLab/CBIG/blob/master/LICENSE.md

    if nargin == 0 % If no input for num_rotations, set default num_rotations as 1000
        num_rotations = 1000;
    end