Yes, some sort of cross-validation would be great, but a) I wouldn't know how to implement it, and b) this thing runs slowly enough as it is!

Let me also raise a substantive issue.  Within groups there is more agreement about what is status-worthy than between groups.  While I think the idea that there exists a status ranking across all the students in a school has enough truth to it to merit the work being done on it, this approach is also obscuring the large differences in what earns you status in different contexts.  A focus on the causes and consequences of status differences (status as defined in this paper) inevitably ignores the importance of groups.  Of course, there are ways of trying to address the existence of groups that complement the work done here, and maybe its not even as hard as I'm making it out to be, but you always have to draw the line somewhere, and at that point you start waving your hands.  I guess I'm just saying we have to do our best to be honest with ourselves and our audience about the many things that might be important but we don't know for sure because we can't fit them in our model.




On Sat, Oct 6, 2012 at 4:22 PM, Trevor Smith <trevorsummerssmith@gmail.com> wrote:
Pong. I am here and I am engaged. I have very much been enjoying reading this discussion. Been busy with other stuff.

Will comment with some thoughts when I get a chance next week. Please keep the conversation going though.

Trevor

On Sat, Oct 6, 2012 at 5:15 PM, Michael Bishop <michaelbish@gmail.com> wrote:
Well it may just be you and me Eric.  And you can feel free to dropout at any time.  Though I assume that Andrew and Trevor are on this list and I know they are somewhat engaged.

This part of the paper explains a few things:

and suppose we believe there to be a ranking of the in- dividuals implied by the pattern of the unreciprocated friendships so that most such friendships run from lower to higher rank. One possible way to infer that ranking would be simply to ignore any reciprocated friendships and then construct a minimum violations ranking of the remaining network [7, 8]. That is, we find the ranking of the network nodes that minimizes the number of connec- tions running from higher ranked nodes to lower ranked ones. In practice this approach works quite well: for the networks studied in this paper the minimum viola- tions rankings have an average of 98% of their unrecipro- cated friendships running from lower to higher ranks and only 2% running the other way. By contrast, versions of the same networks in which edge directions have been randomized typically have about 10% of edges running the wrong way. (Statistical errors in either case are 1% or less, so these observations are highly unlikely to be the results of chance.) The minimum violations ranking, however, misses im-
portant network features because it focuses only on un- reciprocated friendships. In most cases there are a sub- stantial number of reciprocated friendships as well, as many as a half of the total, and they contain significant information about network structure and ranking. For example, as we will see, pairs of individuals who report a reciprocated friendship are almost always closely similar in rank. 

And they can use the minimum violations ranking to seed their maximum likelihood approach.  Without that trick the computational demands would be even more absurd. 

So question, does the fact that they can achieve a ranking with 90% of unreciprocated edges directed from lower to higher status people WHEN THE DATA IS RANDOMLY GENERATED worry you... I mean, its good that they can increase this to 98% when the use the ME, but it seems like they have a lot of flexibility.  I hypothesize that in schools where people fill out their survey more thoroughly (fewer people with very few edges) that they end up with more edges directed the wrong way.  But that the rankings are in some sense truer.  Do you think I'm right?





On Fri, Oct 5, 2012 at 2:44 PM, Eric Purdy <epurdy@uchicago.edu> wrote:
Just out of curiosity, is anybody still reading this thread? What are
people thinking of the listhost so far?

On Fri, Oct 5, 2012 at 11:57 AM, Eric Purdy <epurdy@uchicago.edu> wrote:
> Well, we could just say that we'll do what we want, not use their code
> (except possibly to help us understand the paper), and offer co-author
> credit to them if we manage to get a paper out of it.
>
> In general, being overly generous with co-authorship doesn't usually
> have any bad effects?
>
> On Fri, Oct 5, 2012 at 11:34 AM, Michael Bishop <michaelbish@gmail.com> wrote:
>> well its not published yet.  i think it was conditionally accepted and
>> probably won't come out until the spring.  i'm currently operating under the
>> assumption that i can't publish using their ranking without there say so.
>> since they said they were planning on doing things similar to what i was
>> planning on doing, and they gave me their code before others have access to
>> it (i think), i probably need to consider them coauthors.
>>
>> but now that i've got the code, its not clear how much more help i need or
>> could get from them.  therefore i feel like i'm in a grey area where given
>> my plans, giving them co-authorship seems generous, but giving them nothing
>> more than an acknowledgement seems sorta wrong as well.
>>
>>
>>
>> On Fri, Oct 5, 2012 at 11:04 AM, Eric Purdy <epurdy@uchicago.edu> wrote:
>>>
>>> On Fri, Oct 5, 2012 at 10:13 AM, Michael Bishop <michaelbish@gmail.com>
>>> wrote:
>>> > If I open a second instance of cygwin and run another instance of this
>>> > program, will windows/cygwin know to execute it on a separate core?
>>> > Brian
>>> > (the author) just sent me his timings (attached) to give me an idea
>>> > about
>>> > what to expect.  #3 is the shortest, #50 is the longest.
>>>
>>> Probably that would work? I know very little about windows.
>>>
>>> > Yeah I don't really know what the norms are surrounding this sorta
>>> > thing.  I
>>> > really don't want to send these guys a huge fuck-you.  But it is
>>> > basically
>>> > accepted at a real journal... this new one I think?  Does its going to
>>> > press
>>> > change anything?
>>>
>>> If it's already published, then we can do whatever we want. And we're
>>> not the referees, which is where the real fuck-yous come in. Maybe we
>>> should ask them??
>>>
>>> > Its good to hear their approach seems fairly reasonable to you.  It
>>> > seemed
>>> > weird to me to bring periodic functions like cosine into it... my
>>> > intuition
>>> > is that the density for unreciprocated ties would achieve perhaps 3
>>> > local
>>> > maxima... one somewhere in the middle, and the two "corner solutions" at
>>> > max
>>> > rank differences.
>>>
>>> Yes, the periodicity is a very weird assumption. That's exactly why I
>>> was saying polynomials made more sense to me.
>>>
>>> > I have another friend who suggested eliminating á and â as separate
>>> > parameters, i.e. don't assume reciprocated ties and unreciprocated ties
>>> > are
>>> > different, just allow that to emerge... so he suggested a mixture of 3
>>> > beta
>>> > distributions.
>>>
>>> If you use polynomials like I suggested, then there's no real
>>> difference between alpha and beta being separate or being together. It
>>> is possibly helpful at a conceptual level to separate out the parts
>>> that are symmetric and anti-symmetric, because they tell you about
>>> reciprocated and unreciprocated friendships, respectively.
>>>
>>> --
>>> -Eric
>>
>>
>
>
>
> --
> -Eric



--
-Eric


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