a life in 42 seconds

Friday May 22, 2009

Filed under: general — jackman @ 9:51 am

Gruber linked to this video short by Chris Milk, “Last Day Dream” .

I found it both lovely and unsettling.

Maybe because, like, dude, is that Pauly Shore at 0:21?

Yes it is (screen shot, closing credits):

Picture 2-11

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cut in JAGS?

Wednesday May 13, 2009

Filed under: computing,statistics — jackman @ 3:58 pm

Will Bullock asks:

Offhand, do you know if there’s a way in JAGS to replicate the cut() function that’s available in WinBUGS (page 40)? I’m trying to estimate two separate models within the same JAGS model, with the parameter estimates from the first model being used to produce the data values for the second model. Without something akin to the cut() function, estimation of the second model will affect estimation of the first model, which I don’t want.

And I replied:

I don’t know for sure. It is a good question. I tend to think not, but a good look at the JAGS manual is called for. there is a lot there…

can the data{} block help you? Martyn talks about at p30 of the JAGS manual. if you had the parameters of a posterior density for, from a previous run, you could put those in the data step. but I think that is about as close as you can get.

And then there is the whole issue of whether you want to be doing “cut” at all… Even the WinBUGS authors seem a little ambivalent about it. I’ve done things with it; e.g., measurement models where you want to separate the “measurement” model from some “downstream” model in which the latent quantity being measured appears as a predictor of something else, say, z. But if you believe the model, then z should be allowed to contribute information to the latent stuff being measured, in general (imho).

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Specter (D PA) vs Specter (R PA)

Sunday May 10, 2009

Filed under: politics,statistics — jackman @ 9:43 pm

The “quasi-real-time” rollcall data being maintained by Jeff Lewis (PoliSci, UCLA) is rightly treating Specter (D PA) as a separate legislator, with the voting history of Specter (R PA) now closed. The “new” Specter has 14 recorded roll calls. Treating everyone else as having just one ideal point, we get the following picture (thumbnail below).

Specter (D) is a fairly conservative “D”, but he’s get 10 Democrats to his right; note that with just 14 votes we don’t estimate the ideal point of Specter (D) with much precision. More votes will make the picture clearer. Specter (R) had just two Republicans to his left (the Maine senators).


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