question about tuples @Nick Cox

[Raymond Zhang]

@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.

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,

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.

[daniel klein]

For this particular problem, I would not use tuples at all. I would simply

foreach x in x1 x2 x3 x4 {
    do_something_with `x'
    do_something_with `x' x5
}

If you insist on using tuples, alternatives incliude

tuples x1 x2 x3 x4 x5 , conditionals(!(1&(2|3|4)|2&(3|4)|3&4))

is possible. I find your code easier to read.*


* Also, in the current version of tuples, the results we obtain with my code differ between the Mata-based and the Python-based method. I am working on a fix (for the Mata-based method).

[Raymond Zhang]

dear Daniel, the code above is just an easiest example.what I want is

 global m x1 x2 x3 x4 x5 x6 x7 x8 x9 x10 x11 x12 x13 x14 x15 x16 x17 x18

I want each tuple contains only one of x1 x2 x3 x4，so I think the foreach command may not work.I have to use tuples.

[daniel klein]

Then, perhaps something along the lines

tuples x5 x6 x7 x8 x9 x10 x11 x12 x13 x14 x15 x16 x17 x18

foreach x in x1 x2 x3 x4 {
    forvalues i = 1/`ntuples' {
        [i]do_something_with `tuple`i'' `x'
    }
}

I cannot think of a convenient (and better readble) way to set up the conditionals() option. Note that tuples has a max() option that might be useful for approaches that built on my suggestion.

[Raymond Zhang]

dear Daniel，thanks a lot for your help.
it helps me a lot.