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: CorrClusTh.m
    path of file: ./repos/ExploreASL/External/SPMmodified/xASL
    
    the code of the file until where you have to start completion: function varargout = CorrClusTh(SPM,u,alpha,guess)
% Find the corrected cluster size threshold for a given alpha
%
% FORMAT: function [k,Pc] = CorrClusTh(SPM,u,alpha,guess)
%
% INPUT:
% SPM   - SPM data structure
% u     - Cluster defining threshold
%         If less than zero, u is taken to be uncorrected P-value
% alpha - FWE-corrected level (defaults to 0.05)
% guess - Set to NaN to use a Newton-Rhapson search (default)
%         Or provide a explicit list (e.g. 1:1000) of cluster sizes to
%         search over.
%         If guess is a (non-NaN) scalar nothing happens, except the the
%         corrected P-value of guess is printed. 
%
% OUTPUT: n/a
%
% DESCRIPTION: Finds the corrected cluster size (spatial extent) threshold for a given
%              cluster defining threshold u and FWE-corrected level alpha. 
%
% EXAMPLE:     n/a
%
%_________________________________________________________________________

    
function varargout = CorrClusTh(SPM,u,alpha,guess)
% Find the corrected cluster size threshold for a given alpha
%
% FORMAT: function [k,Pc] = CorrClusTh(SPM,u,alpha,guess)
%
% INPUT:
% SPM   - SPM data structure
% u     - Cluster defining threshold
%         If less than zero, u is taken to be uncorrected P-value
% alpha - FWE-corrected level (defaults to 0.05)
% guess - Set to NaN to use a Newton-Rhapson search (default)
%         Or provide a explicit list (e.g. 1:1000) of cluster sizes to
%         search over.
%         If guess is a (non-NaN) scalar nothing happens, except the the
%         corrected P-value of guess is printed. 
%
% OUTPUT: n/a
%
% DESCRIPTION: Finds the corrected cluster size (spatial extent) threshold for a given
%              cluster defining threshold u and FWE-corrected level alpha. 
%
% EXAMPLE:     n/a
%
%_________________________________________________________________________
% $Id: CorrClusTh.m,v 1.10 2006/05/08 15:31:02 nichols Exp $ Thomas Nichols, Marko Wilke

    epsP = 1e-6;   % Corrected P-value convergence criterion (fraction of alpha)
    du   = 1e-6;   % Step-size for Newton-Rhapson
    maxi = 100;    % Maximum interations for refined search


    if nargin<1 | isempty(SPM)
      load(spm_get(1,'SPM.mat', 'Select SPM.mat to check'));
    end