GPT答：

https://ask.gongduoduo.com

例子1：
```matlab
A = zeros(19, 19);
for i = 1:19
    for j = 1:19
        A(i, j) = i * j;
    end
end
disp(A);
```

例子2：
```matlab
B = zeros(19, 19);
for i = 1:19
    for j = 1:19
        B(i, j) = sin(i) + cos(j);
    end
end
disp(B);
```

例子3：
```matlab 
C= zeros(19, 19); 
for i=1:9 
   for j=10:18 
      C(i,j)=i+j; 
   end 
end 

disp(C);