Archive for Christchurch

no haggis for Burns night!

Posted in Statistics with tags , , , , , , , , , , , , , , , on January 25, 2021 by xi'an

“one of New Zealand’s darkest days”

Posted in Mountains, pictures, Travel with tags , , , , on March 15, 2019 by xi'an

the luminaries [book review]

Posted in Books, Kids, Mountains, Travel with tags , , , , , , , , on April 18, 2015 by xi'an

I bought this book by Eleanor Catton on my trip to Pittsburgh and Toronto in 2013 (thanks to Amazon associates’ gains!), mostly by chance (and also because it was the most recent Man Booker Prize). After a few sleepless nights last week (when I should not have been suffering from New York jet lag!, given my sleeping pattern when abroad), I went through this rather intellectual and somewhat contrived mystery. To keep with tradition (!), the cover was puzzling me until I realised those were phases of the moon, in line with [spoiler!] the zodiacal underlying pattern of the novel, pattern I did not even try to follow for it sounded so artificial. And presumably restricted the flow of the story by imposing further constraints on the characters’ interactions.

The novel has redeeming features, even though I am rather bemused at it getting a Man Booker Prize. (When compared with, say, The Remains of the Day…) For one thing, while a gold rush story of the 1860’s, it takes place on the South Island of New Zealand instead of Klondike, around the Hokitika gold-field, on the West Coast, with mentions of places that brings memory of our summer (well, winter!) visit to Christchurch in 2006… The mix of cultures between English settlers, Maoris, and Chinese migrants, is well-documented and information, if rather heavy at times, bordering on the info-dump, and a central character like the Maori Te Rau Tauwhare sounds caricaturesque. The fact that the story takes place in Victorian times call Dickens to mind, but I find very little connection in either style or structure, nor with Victorian contemporaries like Wilkie Collins, and Victorian pastiches like Charles Palliser‘s Quincunx…. Nothing of the sanctimonious and moral elevation and subtle irony one could expect from a Victorian novel!

While a murder mystery, the plot is fairly upside down (or down under?!): the (spoiler!) assumed victim is missing for most of the novel, the (spoiler!) extracted gold is not apparently stolen but rather lacks owner(s), and the most moral character of the story ends up being the local prostitute. The central notion of the twelve men in a council each bringing a new light on the disappearance of Emery Staines is a neat if not that innovative literary trick but twelve is a large number which means following many threads, some being dead-ends, to gather an appearance of a view on the whole story. As in Rashomon, one finishes the story with a deep misgiving as to who did what, after so many incomplete and biased accountings. Unlike Rashomon, it alas takes forever to reach this point!

Posterior expectation of regularly paved random histograms

Posted in Books, Statistics, University life with tags , , , , , , , , , on October 7, 2013 by xi'an

Today, Raazesh Sainudiin from the University of Canterbury, in Christchurch, New Zealand, gave a seminar at CREST in our BIP (Bayesians in Paris) seminar series. Here is his abstract:

We present a novel method for averaging a sequence of histogram states visited by a Metropolis-Hastings Markov chain whose stationary distribution is the posterior distribution over a dense space of tree-based histograms. The computational efficiency of our posterior mean histogram estimate relies on a statistical data-structure that is sufficient for non-parametric density estimation of massive, multi-dimensional metric data. This data-structure is formalized as statistical regular paving (SRP). A regular paving (RP) is a binary tree obtained by selectively bisecting boxes along their first widest side. SRP augments RP by mutably caching the recursively computable sufficient statistics of the data. The base Markov chain used to propose moves for the Metropolis-Hastings chain is a random walk that data-adaptively prunes and grows the SRP histogram tree. We use a prior distribution based on Catalan numbers and detect convergence heuristically. The L1-consistency of the the initializing strategy over SRP histograms using a data-driven randomized priority queue based on a generalized statistically equivalent blocks principle is proved by bounding the Vapnik-Chervonenkis shatter coefficients of the class of SRP histogram partitions. The performance of our posterior mean SRP histogram is empirically assessed for large sample sizes simulated from several multivariate distributions that belong to the space of SRP histograms.

The paper actually appeared in the special issue of TOMACS Arnaud Doucet and I edited last year. It is coauthored by Dominic Lee, Jennifer Harlow and Gloria Teng. Unfortunately, Raazesh could not connect to our video-projector. Or fortunately as he gave a blackboard talk that turned to be fairly intuitive and interactive.

Season’s Greetings from UC, Christchurch

Posted in Statistics with tags , , , on December 25, 2012 by xi'an

UC 2012 Season greeting cardA kind message I received from the University of Canterbury, Christchurch:

On behalf of the University of Canterbury, best wishes for the festive season.

This year has been challenging for UC, as it has for many organisations. But with work on campus remediation well and truly underway, a busy enrolment period and a recent commitment from the Government to support us in our recovery, we can take heart that the University is making good progress following the events of the past couple of years.

We believe that a strong university goes hand in hand with a robust, cohesive and growing economy and community. We are committed to supporting the recovery of Christchurch through closer partnerships with the business sector, secondary schools, Ngai Tahu, partner institutions, other tertiary education providers and crown research institutes.

Another important component of our plan for the future is a commitment to engage in Christchurch´s new central city health precinct, reflecting our vision of a university that isn’t just a place students come to when they want a degree; but a university that is a learning environment well connected with its communities.

I hope you will have the opportunity over the holiday period to relax, reflect on the year and look ahead.

Please accept my personal thanks for your interest in and support for the University this year. It has made a difference.

Dr Rod Carr Vice-Chancellor