On 24th September 2019 the New South Wales branch gathered on the

campus Macquarie University in north-western Sydney. Members of

the council with offices in the inner suburbs had their Opal cards

and transport apps kept busy in the race to out to North Ryde for

their pre-talk monthly meeting. The writer of this article was declared

the winner, making it door to door in just 45 minutes.

After some high quality hors d'oeuvres the audience sat down to

listen to Dr Pierre Lafaye de Micheaux of the School of Mathematics

and Statistics, University of New South Wales, deliver a presentation

titled "A notion of depth for curve data", which uses ideas from

Princeton statistician John Tukey from the 1970s concerning, for

example, half-space depth for point clouds.

Pierre's research in this area is motivated by data from the

Older Australian Twins Study. There is strong evidence that the

quality of brain fibres impacts quality of life and, therefore,

high quality analyses of brain fibre data is important. The

data are curves in three dimensions so Pierre has had to

extend data depth ideas to this setting. The presenter made

excellent use of three dimensional graphics to visualise

the data and explain the depth concepts.

Another key idea was the concept of parametrised curves

and this involved some elegant geometry-type mathematics

including, of course, the Frechet metric.

After a theoretical exposition Pierre demonstrated his

breadth as a statistician by telling everyone about his

co-authored R package named curveDepth.

Apart from data from the Older Australian Twins Study the

methodology was applied to cyclone paths in the Gulf of Mexico.

The new methodology leads to better detection of outlier cyclones

and better confidence regarding regions at risk. For the brain

fibre applications, an upcoming challenge is to go from data

on 68 brains to 20,000 brains.

Matt Wand

University of Technology Sydney