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: agreement.m
    path of file: ./repos/fieldtrip/external/bct
    
    the code of the file until where you have to start completion: function D = agreement(ci,buffsz)
%AGREEMENT      agreement matrix from clusters
%
%   D = AGREEMENT(CI) takes as input a set of vertex partitions CI of
%   dimensions [vertex x partition]. Each column in CI contains the
%   assignments of each vertex to a class/community/module. This function
%   aggregates the partitions in CI into a square [vertex x vertex]
%   agreement matrix D, whose elements indicate the number of times any two
%   vertices were assigned to the same class.
%
%   In the case that the number of nodes and partitions in CI is large

    
function D = agreement(ci,buffsz)
%AGREEMENT      agreement matrix from clusters
%
%   D = AGREEMENT(CI) takes as input a set of vertex partitions CI of
%   dimensions [vertex x partition]. Each column in CI contains the
%   assignments of each vertex to a class/community/module. This function
%   aggregates the partitions in CI into a square [vertex x vertex]
%   agreement matrix D, whose elements indicate the number of times any two
%   vertices were assigned to the same class.
%
%   In the case that the number of nodes and partitions in CI is large
%   (greater than ~1000 nodes or greater than ~1000 partitions), the script
%   can be made faster by computing D in pieces. The optional input BUFFSZ
%   determines the size of each piece. Trial and error has found that
%   BUFFSZ ~ 150 works well.
%
%   Inputs,     CI,     set of (possibly) degenerate partitions
%               BUFFSZ, optional second argument to set buffer size
%
%   Outputs:    D,      agreement matrix
%
%   Richard Betzel, Indiana University, 2012
%

%modification history
%09.24.2012 - added loop for big N that makes the function slower but also
% prevents it from maxing out memory.

n = size(ci,2);

if nargin < 2
    buffsz = 1000;
end