matlab中怎样计算两个集合的差集?-setdiff函数

 1 >> a=randperm(10);
 2 >> a
 3 
 4 a =
 5 
 6      4    10     7     5     2     6     8     9     1     3
 7 
 8 >> b=a(4:6);
 9 >> b
10 
11 b =
12 
13      5     2     6
14 
15 >> c=setdiff(a,b);
16 >> c
17 
18 c =
19 
20      1     3     4     7     8     9    10