Re: st: inlist() equivalent for mata?

[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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