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: xASL_im_CreateSliceGradient.m
    path of file: ./repos/ExploreASL/Functions/ImageProcessing
    
    the code of the file until where you have to start completion: function xASL_im_CreateSliceGradient(x)
% xASL_im_CreateSliceGradient
%
% FORMAT:       xASL_im_CreateSliceGradient(x)
% 
% INPUT:        x - ExploreASL x structure (STRUCT, REQUIRED)
%
% OUTPUT:       n/a
% 
% -----------------------------------------------------------------------------------------------------------------------------------------------------
% DESCRIPTION:  1. Create slice gradient in same space as input file
%               2. Reslice slice gradient to MNI (using existing ASL matrix changes from e.g. registration to MNI, motion correction, registration to GM)
%               3. Creating average slice gradient
%
% -----------------------------------------------------------------------------------------------------------------------------------------------------
% EXAMPLE:      ...
%
% BACKGROUND INFORMATION:
%
% When a 2D readout is used with ASL, post-label delay and hence T1 decay
% will be dependent on slice timing.
% Therefore, quantification part needs slice reference to quantify per
% slice and correct for effective post-label delay differences.
%
% This function uses exact same ASL matrix changes that occurred due to
% registration to MNI, motion correction and registration to T1.

    
function xASL_im_CreateSliceGradient(x)
% xASL_im_CreateSliceGradient
%
% FORMAT:       xASL_im_CreateSliceGradient(x)
% 
% INPUT:        x - ExploreASL x structure (STRUCT, REQUIRED)
%
% OUTPUT:       n/a
% 
% -----------------------------------------------------------------------------------------------------------------------------------------------------
% DESCRIPTION:  1. Create slice gradient in same space as input file
%               2. Reslice slice gradient to MNI (using existing ASL matrix changes from e.g. registration to MNI, motion correction, registration to GM)
%               3. Creating average slice gradient
%
% -----------------------------------------------------------------------------------------------------------------------------------------------------
% EXAMPLE:      ...
%
% BACKGROUND INFORMATION:
%
% When a 2D readout is used with ASL, post-label delay and hence T1 decay
% will be dependent on slice timing.
% Therefore, quantification part needs slice reference to quantify per
% slice and correct for effective post-label delay differences.
%
% This function uses exact same ASL matrix changes that occurred due to
% registration to MNI, motion correction and registration to T1.
%
% Script dependencies: SPM12
%
% HJ Mutsaerts, ExploreASL 2016
%
% __________________________________
% Copyright 2015-2021 ExploreASL


%% Administration

xASL_delete(x.P.Pop_Path_SliceGradient);
xASL_delete(x.P.Path_SliceGradient_extrapolated);


%% ------------------------------------------------------------------------------------
%% 1    Create slice gradient in same space as input file
tNII = xASL_io_ReadNifti(x.P.Path_ASL4D);
dim = size(tNII.dat(:,:,:,:,:,:,:,:,:));
dim = dim(1:3);
SGim = zeros(dim);

for iSlice=1:dim(3)
    SGim(:,:,iSlice) = iSlice;
end