Re: st: inlist() equivalent for mata?

[Aljar Meesters <aljar.meesters@gmail.com>]

For this implementation I assume that you only have positive integers.
It is pretty fast and scales nicely in N and T. A caveat is that it
consumes memory based on the largest integers in your list and vector.
Best,

Aljar

*** Begin ***

real colvector vec_inlist(real colvector B, real colvector L){
    real colvector b, l
    real scalar minrows

    // Determine the elements in B
    b = J(max(B), 1, 0)
    b[B] = J(rows(B), 1, 1)

    // Determine the elements in L
    l = J(max(L), 1, 0)
    l[L] = J(rows(L), 1, 1)

    // Combine the combination
    minrows = min((rows(b), rows(l)))
    answer = J(rows(b), 1, 0)
    answer[|1, 1 \ minrows, 1 |] = b[|1, 1 \ minrows, 1 |] :* l[|1, 1
\ minrows, 1 |]

    // Reflect back to B
    answer= answer[B]
    return(answer)
}

*** End ***

2014-03-21 2:09 GMT+01:00 Phil Schumm <pschumm@uchicago.edu>:
> On Mar 20, 2014, at 4:42 PM, Andrew Maurer <Andrew.Maurer@qrm.com> wrote:
>> So with Bsize of 1 billion and Lsize of 100,000, it would effectively do a loop of 1 billion iterations over 100,000 elements.
>
>
> In your original post, you said that "T >> N", where T is the length of list L, and N is the length of list B.  This would appear to be the opposite of what you wrote above.
>
>
>> I still think that there should be a more efficient way to do this than the array method posted.
>
>
> The fastest (and simplest) option is to use -anyof()-, e.g.,
>
>
>     real colvector inlist_anyof(real colvector B, real colvector L)
>     {
>         real scalar                                     i
>         real colvector                                  R
>
>         R = J(rows(B),1,0)
>         for (i=1; i<=rows(B); i++) {
>             if (anyof(L, B[i])) R[i] = 1
>         }
>
>         return(R)
>     }
>
>
> -- Phil
>
>
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