试图访问 x(2)；由于 numel(x)=1，索引超出范围。这个怎么解决呀

n = 50; %种群数量（种群大小）
nd = 4; %函数的维度（针对问题有多少个决策变量）
function [z, g] = test_function(x, nd, num_f)
switch num_f
case 1
aK=[.1957 .1947 .1735 .16 .0844 .0627 .0456 .0342 .0323 .0235 .0246];
bK=[.25 .5 1 2 4 6 8 10 12 14 16];bK=1./bK;
z=sum((aK-((x(1).*(bK.^2+x(2).*bK))./(bK.^2+x(3).*bK+x(4)))).^2);
end
function [Lb, Ub, nest, fitness] = init_data(num_f, nd, n)
if num_f == 1
Lb = -5; %下界
Ub = 5 ;
end
end
fitness = 10^100 * ones(n,1);