matlab中如何给一个矩阵中的某几个特定位置赋值

用sub2ind

>> a=zeros(5); i = [2;3;4]; j = [1;4;2];
>> a(sub2ind(size(a), i, j))=1

a =

0 0 0 0 0
1 0 0 0 0
0 0 0 1 0
0 1 0 0 0
0 0 0 0 0