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Archive for 2017

Days 2&3 at #spatialstatistics2017

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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

Written by Claus

July 12th, 2017 at 3:48 pm

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Day 1 at #spatialstatistics2017

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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).

Written by Claus

July 6th, 2017 at 8:44 am

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New Papers!

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I published two new papers recently! Find the titles and the links to more information below. Happy reading!

  1. Detecting and Modelling Structures on the Micro and the Macro Scales: Assessing Their Effects on Solute Transport Behaviour” – This paper sheds light onto a tricky issue: Is a spatial data-set stationary or not? This paper shows a method that can help to decide to delineate a boundary (“macroscale”) between regions that are at least somewhat more stationary than the entire domain. Furthermore, this paper
    • validates the algorithm based on a data-set where a boundary layer has previously been delineated;
    • demonstrates the effects of the macro structure and the smaller scale heterogeneity (“micro structure”) on solute transport behaviour; The micro structure is modelled by multivariate Gaussian and multivariate non-Gaussian structures.
  2. Estimating a Representative Value and Proportion of True Zeros for Censored Analytical Data with Applications to Contaminated Site Assessment” – True zeros such as no precipitation occur frequently in nature. This is one of the very few studies I know that treats those values statistically meaningfully and is based on a real-world data-set. We applied the methodology on a data-set related to contaminated sites, but this has implications everywhere else.

Written by Claus

June 29th, 2017 at 9:03 pm

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Own Your Writing

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I just posted on claus-haslauer.de about “Own Your Writing!”.

In this post, I

  • discuss how important it is to own what you write, even if it comes at a cost: Knowing technology and money. Also, it seems like publishing has become more complicated than it needs to be on open solutions.
  • play with the new JSON-feed format (in python)
  • Written by Claus

    June 21st, 2017 at 9:48 am

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    Thresholds

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    In my work about spatial dependence, I do see that in different ranges of quantiles, the type of dependence can differ. More generally, this means that thresholds are an important characteristic of environmental systems.

    This is why I think this video that I noticed on kottke.org is so inspiring: sometimes something small leads to a big change — a “threshold” is “jumped over”:

    Written by Claus

    June 7th, 2017 at 3:37 pm

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    Years of Blogging

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    • Manton Reece celebrated 15 years of blogging in March. It turns out that planetwater.org does not date that far back, but almost 11 years of blogging is not nothing either. The details are actually blurry in my mind. Definitely Dayf had started the “boardinger” at some time around 2003, we had used that for a while, and I guess I moved to WordPress in 2006
    • In fact, the WordPress installation at sysprovide has been running and has been upgraded constantly ever since – until last Thursday, when the first outage occurred (at least to my knowledge)
    • If there is one thing certain, it’s that things do change. As does the blogging frequency. I guess there are certain cycles
    • Recently, I started to take claus-haslauer.de as my professional site more seriously, and setup a static page generator (Pelican) that supports Jupyter notebooks. While that is pretty exciting, I do not want to neglect planet water! This is the first post that I am writing and posting with Ulysses and not with my traditional TextMate / MarsEdit combination

    Yay to Independent Blogging!

    I will use the occasion of looking back, following Gabe Weatherhead’s spirit, to give a shout out to independent blogging.

    The following three blogs are in my queue since the beginning of time, none of which are particularly related to water:

    I also admit that I follow a few that are on Gabe’s list, and Gabs himself:

    Written by Claus

    April 9th, 2017 at 8:46 pm

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