@Nick Cox
Dear Nick,now I have 5 variables ,x1 x2 x3 x4 x5.
I want each tuple contains only one of x1 x2 x3 x4.
Code:
global m "x1 x2 x3 x4 x5"
The reslut I want to get is
x1,
x2,
x3,
x4,
x1 x5,
x2 x5,
x3 x5,
x4 x5

how can I set the conditional( ) option?
I try to write the cond() like this below,
Code:
global m "x1 x2 x3 x4 x5"
tuples $m,cond(!(1&2) !(2&3) !(1&4) !(1&3) !(2&4) !(3&4)) display

tuple1: x5
tuple2: x4
tuple3: x3
tuple4: x2
tuple5: x1
tuple6: x4 x5
tuple7: x3 x5
tuple8: x2 x5
tuple9: x1 x5
But this code is a little complicated.
Do you have another easier method?

Many thanks in advance.