## Archive for July, 2017

## Days 2&3 at #spatialstatistics2017

It became increasingly difficult to post updates on the spatial statistics conference. The icebreaker, another day full with diverse interesting talks, the dinner, another day that ended the conference with an interesting session honouring the achievements of Peter Diggle. Former and current colleagues such as Paulo Ribeiro and Emanuel Giorgi gave enlightening talks that stressed both the scientific achievements and the great kindness and humanity of Peter Diggle. CHICAS, the center for health informatics, computing, and statistics, is the current culmination of his efforts.

It’s hard to pick topics that stood out during the last two days of the conference, just because there were many great talks on a large variety of topics. Here is an attempt.

## Point Processes

There were a number of talks covering Point Processes, notably the keynotes by Thordis Thorarinsdottir and Rasmus Waagepetersen. Thordis had a variety of interesting quotes including this one by Frank H Bigelow from 1905:

There are three processes that are generally essential for the complete development of any branch of science, and they must be accurately applied before the subject can be considered to be satisfactorily explained. The first is the discovery of a mathematical analysis, the second is the discussion of numerous observations, and the third is a correct application of the mathematics to the observations, including a demonstration that these are in agreement.

Thordis urged the need for more and better inference methods. I might be worth pointing out that Bigelow went on to state that

Often a good theory is misapplied to good observations, or good observations are explained by a poor theory.

In summary, these thoughts are not too far away from Peter Diggle’s triangle, pictured above.

## Copulas

There were two nice talks that employed copulas for multivariate spatial models and one that I missed, unfortunately:

- Jonathan Tawn from the University of Lancaster presented on “
*Modelling Spatial Extreme Events*“; he takes great care of marginal distributions and how to reasonably include extremes there for a better joint representation in copula space; - Fakhereh Alidoost and Alfred Stein from the University of Twente presented on “
*Interpolation of Daily Mean Air Temperature Data via Spatial and Non-Spatial Copulas*” - the talk that I missed was entitled “
*Hierarchical Copula Regression Models for Areal Data*” presented by D. Musgrove, J. Hughes and L. Eberly

## Various

- Denis Allard presented on weather generators, the issues related to different dependence structures in the variables included typically, and advertised a workshop on stochastic weather generators coming up in Berlin.
- Ricardo Carrizo Vergara, a student of Denis Allard, is investigating the relationship between SPDEs and geostatistics.
- Pierre Goovaerts showed his insight into the Flint water crisis, which is published in three papers (1, 2, 3).

## Day 1 at #spatialstatistics2017

Peter Atkinson opened the conference with pointing out the broad scope of the conference: “one health” (e.g., CDC, UC Davis) that relates to human, veterinary, and environmental health. I was glad that my talk with interpolating groundwater quality data fit right into that scope.

I saw too many interesting talks and met too many interesting and nice people, to list everything here. Instead, this is a small selection.

## Connections

First off, it’s nice to encounter similarly minded work. Particularly, I was happy to see the following presentations:

- Emilie Chautru presented a poster entitled “Cokriging of Nonnegative Data on the L1 Sphere”, on Cokriging compositional data;
- Svenia Behm from the University of Passau presented a talk entitled “Statistical Inference in the RIO Model – the Detrending Step Revisited”. She calculates something similar to my “locally mixed distributions”;
- A. Lawson pointed out the importance of properly taking censored measurements and true zeros into account, both in his keynote (“One Health: Spatial Statistics at the Border of Human and Veterinary Health”) and in his talk (“Bayesian Cure-Rate Survival Model With Spatially Structured Censoring”). I didn’t talk about it at this conference, but it is dear to my heart;

## Cool Stuff

- M. Pereira showed cool images of road crash density estimates based on data from Paris, France. Benedikt Gräler showed a poster with the Envirocar initiative. Data related to driving patterns and fuel consumption is collected while driving, is analysed, and can be viewed online.
- Samir Bhatt gave a great keynote presentationon mapping malaria endemicity. Besides the interesting issues related directly to malaria, this talk raised some interesting questions on modelling philosophies. Samir Bhatt proposed “richer models” as a way forward beyond his current practice of using multivariate models. Alternatively, he phrased it as models that “include mechanisms”. Peter Diggle asked how his approach relates to the concept of parsimonity. It is interesting to me that Samir Batt suggests to include mechanistic models in his data driven models, whereas for the groundwater quality mapping project I am working on, I have moved to a stochastic model. On the scale of the state, I see that deterministic, pde-based models are not feasible (too many unknown parameters and processes).