粒子群算法时为什么程序说适应度函数无法执行赋值，因为左侧的索引与右侧的大小不兼容。

ennn我有8 个参数

clc
clear
c1 = 1.49445;
c2 = 1.49445;
maxgen = 1000;   % 进化次数
sizepop = 50;   %种群规模
Vmax = 1;
Vmin = -1;
popmax = 100;
popmin = 0;
% 产生初始粒子和速度
for i = 1:sizepop
    % 随机产生一个种群
    pop(i,:) = 5*rands(1,8);    %初始种群
    V(i,:) = rands(1,8); %初始化速度
    % 计算适应度
    fitness(i) = fun(pop(i,:));   %染色体的适应度
end

%个体极值和群体极值
[bestfitness bestindex] = max(fitness);
zbest = pop(bestindex,:);   %全局最佳
gbest = pop;    %个体最佳
fitnessgbest = fitness;   %个体最佳适应度值
fitnesszbest = bestfitness;   %全局最佳适应度值

%迭代寻优
for i = 1:maxgen

    for j = 1:sizepop
        % 速度更新
        w(i)=0.9+0.5*(2*i/200-(i/200)^2);
        V(j,:) = w(i)*V(j,:) + c1*rand*(gbest(j,:) - pop(j,:)) + c2*rand*(zbest - pop(j,:));
        V(j,find(V(j,:)>Vmax)) = Vmax;
        V(j,find(V(j,:)<Vmin)) = Vmin;

        % 种群更新
        pop(j,:) = pop(j,:) + V(j,:);
        pop(j,find(pop(j,:)>popmax)) = popmax;
        pop(j,find(pop(j,:)<popmin)) = popmin;

        % 适应度值更新
        fitness(j) = fun(pop(j,:));
    end

    for j = 1:sizepop
        % 个体最优更新
        if fitness(j) > fitnessgbest(j)
            gbest(j,:) = pop(j,:);
            fitnessgbest(j) = fitness(j);
        end

        % 群体最优更新
        if fitness(j) > fitnesszbest
            zbest = pop(j,:);
            fitnesszbest = fitness(j);
        end
    end
    yy(i) = fitnesszbest;
end
%.输出结果
[fitnesszbest, zbest]
plot3(zbest(1), zbest(2), fitnesszbest,'bo','linewidth',1.5)

figure
plot(yy)
title('最优个体适应度','fontsize',12);
xlabel('进化代数','fontsize',12);ylabel('适应度','fontsize',12);
function y=fun(x);
load('UIt_2.mat', 'UI')
load('UIt_2.mat', 'du')
U=UI(1,:);
I=UI(2,:);
p=100*pi*8/9*i;

y=sum(I-(x(1).*U+x(2).*U.^3+x(3).^du+3.*x(4).*du.*U.^2+U./(1./(x(5)+x(6).*((1./(1+p).^2).*(U.^2+du.^2)))+1./(100.*pi.*i.*(x(7)+x(8).*((1./(1+1./p).^2).*(U.^2+du.^2)))))));
y=abs(y);
end