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: maroi_matrix.m
    path of file: ./repos/malini/Codes/deconvolution - model/spm8/marsbar-0.44/@maroi_matrix
    
    the code of the file until where you have to start completion: function [o, others] = maroi_matrix(params, space)
% maroi_matrix - class constructor
% There are two usual forms of the call:
% 1) Constructor call: obj = maroi_matrix(params);
% where input is [defaults]

    
function [o, others] = maroi_matrix(params, space)
% maroi_matrix - class constructor
% There are two usual forms of the call:
% 1) Constructor call: obj = maroi_matrix(params);
% where input is [defaults]
%  params  - a structure containing any fields for a maroi parent and
%            .dat - a matrix
%            .mat - mapping of matrix indices to mm
%
% 2) Rebase call: obj = maroi_matrix(obj, space)
% where input is [defaults]
%  obj - a maroi_matrix object
%  space - mars_space object defining space to reslice to
%
% This maroi_matrix object is used for conversion between
% different types of rois, and for combining rois
% Much of the work is in the converter routines for other roi objects, to
% return objects of this type
%
% $Id$

myclass = 'maroi_matrix';
defstruct = struct('dat', [],'mat', eye(4));

if nargin < 1
  params = [];
end