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: spm_fp_fmin.m
    path of file: ./repos/ExploreASL/External/SPMmodified
    
    the code of the file until where you have to start completion: function [P] = spm_fp_fmin(M)
% optimises the parameters with respect to an equilibrium density
% FORMAT [P] = spm_fp_fmin(M)
%

    
function [P] = spm_fp_fmin(M)
% optimises the parameters with respect to an equilibrium density
% FORMAT [P] = spm_fp_fmin(M)
%
% M   - model structure with desired density specified by M(1).fq and
%       support specified by M(1).X = spm_ndgrid(x)
%
% P   - optimised parameters
%
%--------------------------------------------------------------------------
% This routine uses EM (spm_nlsi_NG) and the Fokker Planck formulation to
% minimise the difference between the flow and dispersion terms induced by
% the free parameters of the flow (M(1),f).
%__________________________________________________________________________
% Copyright (C) 2005 Wellcome Trust Centre for Neuroimaging
 
% Karl Friston
% $Id: spm_fp_fmin.m 4136 2010-12-09 22:22:28Z guillaume $
 
 
% specify function returning the flow-depend