can you change the % Multi-objective function from switch to be more like this, i want to try zdt1 function:


function f = zdt1(x)
    f1 = x(1);
    g = 1 + 9 * sum(x(2:end)) / (length(x) - 1);
    h = 1 - sqrt(f1 / g);
    f2 = g * h;
    f = [f1, f2];
end


the code:
% ----------------------------------------------------------------------- %
% Example of use of the funcion NSGAII.m, which performs a Non Sorting Gene-
% tic Algorithm II (NSGA-II), based on Deb2002.                           %
% ----------------------------------------------------------------------- %
%   Author:  Victor Martinez Cagigal                                      %
%   Date:    22/12/2017                                                   %
%   E-mail:  vicmarcag (at) gmail (dot) com                               %
% ----------------------------------------------------------------------- %
%   References:                                                           %
%    [1] Deb, K., Pratap, A., Agarwal, S., & Meyarivan, T. A. M. T. (2002)%
%        A fast and elitist multiobjective genetic algorithm: NSGA-II.    %
%        IEEE transactions on evolutionary computation, 6(2), 182-197.    %
% ----------------------------------------------------------------------- %
clear all; clc; close all;

% Multi-objective function
%MultiObjFnc = 'ZDT1';
%MultiObjFnc = 'ZDT2';
MultiObjFnc = 'ZDT3';
%MultiObjFnc = 'ZDT6';

switch MultiObjFnc
    case 'ZDT1'             % ZDT1 (convex)
        g = @(x) 1+9.*sum(x(:,2:end),2)./(size(x,2)-1);
        MultiObj.fun = @(x) [x(:,1), g(x).*(1-sqrt(x(:,1)./g(x)))];
        MultiObj.nVar = 30; 
        MultiObj.var_min = zeros(1,MultiObj.nVar);
        MultiObj.var_max = ones(1,MultiObj.nVar);
        load('ZDT1.mat');
        MultiObj.truePF = PF;
    case 'ZDT2'             % ZDT2 (non-convex)
        f = @(x) x(:,1);
        g = @(x) 1+9.*sum(x(:,2:end),2)./(size(x,2)-1);
        h = @(x) 1-(f(x)./g(x)).^2;
        MultiObj.fun = @(x) [f(x), g(x).*h(x)];
        MultiObj.nVar = 30; 
        MultiObj.var_min = zeros(1,MultiObj.nVar);
        MultiObj.var_max = ones(1,MultiObj.nVar);
        load('ZDT2.mat');
        MultiObj.truePF = PF;
    case 'ZDT3'             % ZDT3 (discrete)
        f = @(x) x(:,1);
        g  = @(x) 1+(9/(size(x,2)-1)).*sum(x(:,2:end),2);
        h  = @(x) 1 - sqrt(f(x)./g(x)) - (f(x)./g(x)).*sin(10.*pi.*f(x));
        MultiObj.fun = @(x) [f(x), g(x).*h(x)];
        MultiObj.nVar = 30;
        MultiObj.var_min = 0.*ones(1,MultiObj.nVar);
        MultiObj.var_max = 1.*ones(1,MultiObj.nVar);
        load('ZDT3.mat');
        MultiObj.truePF = PF;
    case 'ZDT6'             % ZDT6 (non-uniform)
        f = @(x) 1 - exp(-4.*x(:,1)).*sin(6.*pi.*x(:,1));
        g = @(x) 1 + 9.*(sum(x(:,2:end),2)./(size(x,2)-1)).^0.25;
        h = @(x) 1 - (f(x)./g(x)).^2;
        MultiObj.fun = @(x) [f(x), g(x).*h(x)];
        MultiObj.nVar = 10;
        MultiObj.var_min = 0.*ones(1,MultiObj.nVar);
        MultiObj.var_max = 1.*ones(1,MultiObj.nVar);
        load('ZDT6.mat');
        MultiObj.truePF = PF;
end

% Parameters
params.Np = 200;        % Population size
params.pc = 0.9;        % Probability of crossover
params.pm = 0.5;        % Probability of mutation
params.maxgen = 100;    % Maximum number of generations
params.ms = 0.05;       % Mutation strength

% NSGA-II algorithm
NSGAII(params,MultiObj);   


function NSGAII(params,MultiObj)

    % Parameters
    Np      = params.Np;        % Number of chromosomes in the population
    maxgen  = params.maxgen;    % Maximum number of generations
    pc      = params.pc;        % Probability of crossover
    pm      = params.pm;        % Probability of mutation
    ms      = params.ms;        % Mutation strength
    fun     = MultiObj.fun;         % Objective function
    nVar    = MultiObj.nVar;        % Number of variables (dimensions or objectives)
    var_min = MultiObj.var_min(:);  % Minimum value for each gen
    var_max = MultiObj.var_max(:);  % Maximum value for each gen
        
    % Initialization
    gen   = 1;
    P     = repmat((var_max-var_min)',Np,1).*rand(Np,nVar) + repmat(var_min',Np,1);
    Pfit  = fun(P);
    Prank = FastNonDominatedSorting_Vectorized(Pfit);
    [P,~] = selectParentByRank(P,Prank);
    Q = applyCrossoverAndMutation(P,pc,pm,ms,var_max,var_min);
    
    % Plotting and verbose
    if(size(Pfit,2) == 2)
        h_fig = figure(1);
        h_par=scatter(Pfit(:,1),Pfit(:,2),20,'filled', 'markerFaceAlpha',0.3,'MarkerFaceColor',[128 193 219]./255); hold on;
        h_rep = plot(Pfit(:,1),Pfit(:,2),'ok'); hold on;
        grid on; xlabel('f1'); ylabel('f2');
        drawnow;
        axis square;
    end
    if(size(Pfit,2) == 3)
        h_fig = figure(1);
        h_rep = plot3(Pfit(:,1),Pfit(:,2),Pfit(:,3),'ok'); hold on;
        grid on; xlabel('f1'); ylabel('f2'); zlabel('f3');
        drawnow;
        axis square;
    end
    display(['Generation #' num2str(gen) ' - First front size: ' num2str(sum(Prank==1))]);
    
    % Main NSGA-II loop
    stopCondition = false;
    while ~stopCondition
        
        % Merge the parent and the children
        R = [P; Q];
        
        % Compute the new Pareto Fronts
        Rfit = real(fun(R));
        Rrank = FastNonDominatedSorting_Vectorized(Rfit);

        % Plotting and verbose
        if(size(Rfit,2) == 2)
            figure(h_fig); delete(h_rep);
            h_par=scatter(Rfit(1:Np,1),Rfit(1:Np,2),20,'filled', 'markerFaceAlpha',0.3,'MarkerFaceColor',[128 193 219]./255); hold on;
            h_rep = plot(Rfit(1:Np,1),Rfit(1:Np,2),'ok'); hold on;
            if(isfield(MultiObj,'truePF'))
                try delete(h_pf); end
                h_pf = plot(MultiObj.truePF(:,1),MultiObj.truePF(:,2),'.','color',0.8.*ones(1,3)); hold on;
            end
            grid on; xlabel('f1'); ylabel('f2');
            drawnow;
            axis square;
        end
        if(size(Rfit,2) == 3)
            figure(h_fig); delete(h_rep);
            h_rep = plot3(Rfit(1:Np,1),Rfit(1:Np,2),Rfit(1:Np,3),'ok'); hold on;
            if(isfield(MultiObj,'truePF'))
                try delete(h_pf); end
                h_pf = plot3(MultiObj.truePF(:,1),MultiObj.truePF(:,2),MultiObj.truePF(:,3),'.','color',0.8.*ones(1,3)); hold on;
            end
            grid on; xlabel('f1'); ylabel('f2');
            drawnow;
            axis square;
        end
        display(['Generation #' num2str(gen) ' - First front size: ' num2str(sum(Rrank==1))]);
        
        
        % Sort by rank 
        [Rrank,idx] = sort(Rrank,'ascend');
        Rfit = Rfit(idx,:);
        R = R(idx,:);
        
        % Compute the crowding distance index
        [Rcrowd,Rrank,~,R] = crowdingDistances(Rrank,Rfit,R);
        
        % Select Parent 
        P = selectParentByRankAndDistance(Rcrowd,Rrank,R);
        
        % Compute child
        Q = applyCrossoverAndMutation(P,pc,pm,ms,var_max,var_min);
        
        % Increment generation
        gen = gen + 1;
        if(gen>maxgen), stopCondition = true; end
    end
end

% Function that selects a new parent based on the crowding distance
% operator
function [newParent] = selectParentByRankAndDistance(Rcrowd,Rrank,R)
    
    % Initialization
    N = length(Rcrowd)/2;
    Npf = length(unique(Rrank));
    newParent = zeros(N,size(R,2));
    
    % Selecting the chromosomes
    pf = 1;
    numberOfSolutions = 0;
    while pf <= Npf
        % If there is enough space, select solutions based on rank
        if numberOfSolutions + sum(Rrank == pf) <= N
            newParent(numberOfSolutions+1:numberOfSolutions+sum(Rrank == pf),:) = R(Rrank == pf,:);
            numberOfSolutions = numberOfSolutions + sum(Rrank == pf);
        % If there isn't enugh space, sort by crowding distances
        else
            rest = N - numberOfSolutions;
            lastPF = R(Rrank == pf,:);
            lastPFdist = Rcrowd(Rrank == pf);
            [~,idx] = sort(lastPFdist,'descend');
            lastPF = lastPF(idx,:);
            newParent(numberOfSolutions+1:numberOfSolutions+rest,:) = lastPF(1:rest,:);
            numberOfSolutions = numberOfSolutions + rest;
        end
        pf = pf + 1;
    end
end

% Function that computes the crowding distances of every single ParetoFront
function [sortCrowd,sortRank,sortFit,sortPop] = crowdingDistances(rank,fitness,pop)

    % Initialize
    sortPop = [];
    sortFit = [];
    sortRank = [];
    sortCrowd = [];
    
    Npf = length(unique(rank));
    for pf = 1:1:Npf
        index = find(rank==pf);
        temp_fit = fitness(index,:);
        temp_rank = rank(index,:);
        temp_pop = pop(index,:);
        
        % Sort by first dimension
        [temp_fit,sort_idx] = sortrows(temp_fit,1);
        temp_rank = temp_rank(sort_idx);
        sortFit = [sortFit; temp_fit];
        sortRank = [sortRank; temp_rank];
        sortPop = [sortPop; temp_pop(sort_idx,:)];
        
        % Crowded distances
        temp_crowd = zeros(size(temp_rank));
        for m = 1:1:size(fitness,2)
            temp_max = max(temp_fit(:,m));
            temp_min = min(temp_fit(:,m));
            for l = 2:1:length(temp_crowd)-1
                temp_crowd(l) = temp_crowd(l) + (abs(temp_fit(l-1,m)-temp_fit(l+1,m)))./(temp_max-temp_min);
            end
        end
        temp_crowd(1) = Inf;
        temp_crowd(length(temp_crowd)) = Inf;
        sortCrowd = [sortCrowd; temp_crowd];
    end
end

% Function that calculates a child population by applying crossover and mutation
function Q = applyCrossoverAndMutation(parent,pc,pm,ms,var_max,var_min)
    % Params
    N = size(parent,1);
    nVar = size(parent,2);
    
    % Child initialization
    Q = parent;
    
    % Crossover
    cross_idx = rand(N,1) < pc;
    cross_idx = find(cross_idx);
    for c = 1:1:length(cross_idx)
        selected = randi(N,1,1);
        while selected == c
            selected = randi(N,1,1);
        end
        cut = randi(nVar,1,1);
        Q(c,:) = [parent(c,1:cut), parent(selected,cut+1:nVar)];
    end
    
    % Mutation population with Gaussian distribution
    mutatedPop = Q + ms.*repmat((var_max-var_min)',N,1).*randn(N,nVar);
    minVal = repmat(var_min',N,1);
    maxVal = repmat(var_max',N,1);
    mutatedPop(mutatedPop<minVal) = minVal(mutatedPop<minVal);
    mutatedPop(mutatedPop>maxVal) = maxVal(mutatedPop>maxVal);
    
    % Mutate the children with probability pm
    mut_idx = rand(N,nVar) < pm;
    Q(mut_idx) = mutatedPop(mut_idx);
end

% Function that performs a binary tournament selection and extracts one
% parent from the initial population based on their ranks.
function [P1,P1rank]   = selectParentByRank(P, Prank)
    % Take the couples
    N = length(Prank);    
    left_idx  = randi(N,N,1);
    right_idx = randi(N,N,1);
    while sum(left_idx==right_idx)>0
        right_idx(left_idx==right_idx) = randi(N,sum(left_idx==right_idx),1);
    end
    
    % Make the tournament
    winners = zeros(N,1);
    winners(Prank(left_idx)<=Prank(right_idx)) = left_idx(Prank(left_idx)<=Prank(right_idx));
    winners(Prank(right_idx)<Prank(left_idx)) = right_idx(Prank(right_idx)<Prank(left_idx));
    
    % Select both populations
    P1 = P(winners,:);
    P1rank = Prank(winners,:);
end

% Funtion that performs a Fast Non Dominated Sorting algorithm of the input
% fitnesses. Note: the code is not vectorized, its programming is just
% based on Deb2002.
function [RANK] = FastNonDominatedSorting_Loop(fitness)
    % Initialization
    Np = size(fitness,1);
    N = zeros(Np,1);
    S{Np,1} = [];
    PF{Np,1} = [];
    RANK = NaN(Np,1);
    
    % Main algorithm
    for p_idx = 1:1:Np
        p = fitness(p_idx,:);
        for q_idx = 1:1:Np
            q = fitness(q_idx,:);
            if dominates(p,q)
                S{p_idx,1} = [S{p_idx,1}; q_idx];
            elseif dominates(q,p)
                N(p_idx) = N(p_idx) + 1;
            end
        end
        if N(p_idx) == 0
            RANK(p_idx) = 1;
            PF{1,1} = [PF{1,1}; p_idx];
        end
    end
    i = 1;
    while ~isempty(PF{i,1})
        Q = [];
        currPF = PF{i,1};
        for p_idx = 1:1:length(currPF)
            Sp = S{currPF(p_idx),1};
            for q_idx = 1:1:length(Sp)
                N(Sp(q_idx)) = N(Sp(q_idx))-1;
                if(N(Sp(q_idx)) == 0)
                    RANK(Sp(q_idx)) = i + 1;
                    Q = [Q; Sp(q_idx)];
                end
            end
        end
        i = i + 1;
        PF{i,1} = Q;
    end
end

% Function that performs a vectorized version of the Fast Non Dominated Sorting
% algorithm which speeds up the computation time
function [RANK] = FastNonDominatedSorting_Vectorized(fitness)
    % Initialization
    Np = size(fitness,1);
    RANK = zeros(Np,1);
    current_vector = [1:1:Np]';
    current_pf = 1;
    all_perm = [repmat([1:1:Np]',Np',1), reshape(repmat([1:1:Np],Np,1),Np^2,1)];
    all_perm(all_perm(:,1)==all_perm(:,2),:) = [];
    
    % Computing each Pareto Front
    while ~isempty(current_vector)
        
        % Check if there is only a single particle
        if length(current_vector) == 1
            RANK(current_vector) = current_pf;
            break;
        end
        
        % Non-dominated particles
            % Note: nchoosek has an exponential grow in computation time, so
            % it's better to take all the combinations including repetitions using a
            % loops (quasi-linear grow) or repmats (linear grow)
            %all_perm = nchoosek(current_vector,2);   
            %all_perm = [all_perm; [all_perm(:,2) all_perm(:,1)]];     
        d = dominates(fitness(all_perm(:,1),:),fitness(all_perm(:,2),:));
        dominated_particles = unique(all_perm(d==1,2));

        % Check if there is no room for more Pareto Fronts
        if sum(~ismember(current_vector,dominated_particles)) == 0
            break;
        end

        % Update ranks and current_vector
        non_dom_idx = ~ismember(current_vector,dominated_particles);
        RANK(current_vector(non_dom_idx)) = current_pf;
        all_perm(ismember(all_perm(:,1),current_vector(non_dom_idx)),:) = [];
        all_perm(ismember(all_perm(:,2),current_vector(non_dom_idx)),:) = [];
        current_vector(non_dom_idx) = [];
        current_pf = current_pf + 1;
    end
end

% Function that returns true if x dominates y and false otherwise
function d = dominates(x,y)
    d = (all(x<=y,2) & any(x<y,2));
end