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: Plotstrain0Quadtree.m
    path of file: ./repos/2D_ALDIC/func_quadtree
    
    the code of the file until where you have to start completion: function [strain_exx,strain_exy,strain_eyy,strain_principal_max,strain_principal_min, ...
    strain_maxshear,strain_vonMises] = Plotstrain0Quadtree(F,coordinatesFEMWorld,elementsFEM,DICpara)
%PLOTSTRAIN0QUADTREE: to plot DIC solved strain fields in a quadtree mesh
%   [strain_exx,strain_exy,strain_eyy,strain_principal_max,strain_principal_min, ...
%    strain_maxshear,strain_vonMises] = Plotstrain0Quadtree(F,coordinatesFEM,elementsFEM)
%
%   INPUT: F                    DIC solved deformation gradient tensor
%          coordinatesFEMWorld  coordinates of each points on the image domain
%          elementsFEM          FE-elements
%          DICpara              chosen DIC parameters
%
%   OUTPUT: strain_exx              strain xx-compoent
%           strain_exy              strain xy-compoent
%           strain_eyy              strain yy-compoent
%           strain_principal_max    max principal strain on the xy-plane
%           strain_principal_min    min principal strain on the xy-plane
%           strain_maxshear         max shear strain on the xy-plane
%           strain_vonMises         equivalent von Mises strain
%
%   Plots:       
%       1) strain sxx
%       2) strain sxy
%       3) strain syy
%       4) max principal strain on the xy-plane 
%       5) min principal strain on the xy-plane
%       6) max shear strain on the xy-plane
%       7) equivalent von Mises strain
%
%
% ----------------------------------------------
% Author: Jin Yang.
% Contact and support: jyang526@wisc.edu -or- aldicdvc@gmail.com
% Last time updated: 2020.12
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    
function [strain_exx,strain_exy,strain_eyy,strain_principal_max,strain_principal_min, ...
    strain_maxshear,strain_vonMises] = Plotstrain0Quadtree(F,coordinatesFEMWorld,elementsFEM,DICpara)
%PLOTSTRAIN0QUADTREE: to plot DIC solved strain fields in a quadtree mesh
%   [strain_exx,strain_exy,strain_eyy,strain_principal_max,strain_principal_min, ...
%    strain_maxshear,strain_vonMises] = Plotstrain0Quadtree(F,coordinatesFEM,elementsFEM)
%
%   INPUT: F                    DIC solved deformation gradient tensor
%          coordinatesFEMWorld  coordinates of each points on the image domain
%          elementsFEM          FE-elements
%          DICpara              chosen DIC parameters
%
%   OUTPUT: strain_exx              strain xx-compoent
%           strain_exy              strain xy-compoent
%           strain_eyy              strain yy-compoent
%           strain_principal_max    max principal strain on the xy-plane
%           strain_principal_min    min principal strain on the xy-plane
%           strain_maxshear         max shear strain on the xy-plane
%           strain_vonMises         equivalent von Mises strain
%
%   Plots:       
%       1) strain sxx
%       2) strain sxy
%       3) strain syy
%       4) max principal strain on the xy-plane 
%       5) min principal strain on the xy-plane
%       6) max shear strain on the xy-plane
%       7) equivalent von Mises strain
%
%
% ----------------------------------------------
% Author: Jin Yang.
% Contact and support: jyang526@wisc.edu -or- aldicdvc@gmail.com
% Last time updated: 2020.12
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% Initialization
warning off; load('colormap_RdYlBu.mat','cMap');

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% convert pixel unit to the physical world unit %%%%%
um2px = DICpara.um2px; 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% Compute strain components

u_x = F(1:4:end