Peter Rousseeuw
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Peter J. Rousseeuw (born 13 October 1956) is a
statistician A statistician is a person who works with theoretical or applied statistics. The profession exists in both the private and public sectors. It is common to combine statistical knowledge with expertise in other subjects, and statisticians may wor ...
known for his work on
robust statistics Robust statistics are statistics with good performance for data drawn from a wide range of probability distributions, especially for distributions that are not normal. Robust statistical methods have been developed for many common problems, suc ...
and
cluster analysis Cluster analysis or clustering is the task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense) to each other than to those in other groups (clusters). It is a main task of ...
. He obtained his PhD in 1981 at the
Vrije Universiteit Brussel The Vrije Universiteit Brussel (VUB) () is a Dutch and English-speaking research university located in Brussels, Belgium.The Vrije Universiteit Brussel is one of the five universities officially recognised by the Flemish Community, Flemish gov ...
, following research carried out at the
ETH (colloquially) , former_name = eidgenössische polytechnische Schule , image = ETHZ.JPG , image_size = , established = , type = Public , budget = CHF 1.896 billion (2021) , rector = Günther Dissertori , president = Joël Mesot , a ...
in Zurich, which led to a book on influence functions. Later he was professor at the
Delft University of Technology Delft University of Technology ( nl, Technische Universiteit Delft), also known as TU Delft, is the oldest and largest Dutch public technical university, located in Delft, Netherlands. As of 2022 it is ranked by QS World University Rankings among ...
, The Netherlands, at the
University of Fribourg The University of Fribourg (french: Université de Fribourg; german: Universität Freiburg) is a public university located in Fribourg, Switzerland. The roots of the university can be traced back to 1580, when the notable Jesuit Peter Canisius ...
, Switzerland, and at the
University of Antwerp The University of Antwerp ( nl, Universiteit Antwerpen) is a major Belgian university located in the city of Antwerp. The official abbreviation is ''UA'', but ''UAntwerpen'' is more recently used. The University of Antwerp has about 20,000 stud ...
, Belgium. Next he was a senior researcher at
Renaissance Technologies Renaissance Technologies LLC, also known as RenTech or RenTec, is an American hedge fund based in East Setauket, New York, on Long Island, which specializes in systematic trading using quantitative models derived from mathematical and statisti ...
. He then returned to Belgium as professor at
KU Leuven KU Leuven (or Katholieke Universiteit Leuven) is a Catholic research university in the city of Leuven, Belgium. It conducts teaching, research, and services in computer science, engineering, natural sciences, theology, humanities, medicine, l ...
, until becoming emeritus in 2022. His former PhD students include Annick Leroy, Hendrik Lopuhaä, Geert Molenberghs, Christophe Croux, Mia Hubert, Stefan Van Aelst, Tim Verdonck and Jakob Raymaekers.


Research

Rousseeuw has constructed and published many useful techniques. He proposed the
Least Trimmed Squares Least trimmed squares (LTS), or least trimmed sum of squares, is a robust statistical method that fits a function to a set of data whilst not being unduly affected by the presence of outliers. It is one of a number of methods for robust regressio ...
method and
S-estimator The goal of S-estimators is to have a simple high-breakdown regression estimator, which share the flexibility and nice asymptotic properties of M-estimators. The name "S-estimators" was chosen as they are based on estimators of scale. We will con ...
s for
robust regression In robust statistics, robust regression seeks to overcome some limitations of traditional regression analysis. A regression analysis models the relationship between one or more independent variables and a dependent variable. Standard types of reg ...
, which can resist
outliers In statistics, an outlier is a data point that differs significantly from other observations. An outlier may be due to a variability in the measurement, an indication of novel data, or it may be the result of experimental error; the latter are ...
in the data. He also introduced the Minimum Volume Ellipsoid and Minimum Covariance Determinant methods for robust scatter matrices. This work led to his book Robust Regression and Outlier Detection with Annick Leroy. With Leonard Kaufman he coined the term
medoid Medoids are representative objects of a data set or a cluster within a data set whose sum of dissimilarities to all the objects in the cluster is minimal. Medoids are similar in concept to means or centroids, but medoids are always restricted to be ...
when proposing the
k-medoids The -medoids problem is a clustering problem similar to -means. The name was coined by Leonard Kaufman and Peter J. Rousseeuw with their PAM algorithm. Both the -means and -medoids algorithms are partitional (breaking the dataset up into group ...
method for
cluster analysis Cluster analysis or clustering is the task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense) to each other than to those in other groups (clusters). It is a main task of ...
, also known as Partitioning Around Medoids (PAM). His
silhouette A silhouette ( , ) is the image of a person, animal, object or scene represented as a solid shape of a single colour, usually black, with its edges matching the outline of the subject. The interior of a silhouette is featureless, and the silhou ...
display shows the result of a cluster analysis, and the corresponding silhouette coefficient is often used to select the number of clusters. The work on cluster analysis led to a book titled Finding Groups in Data. Rousseeuw was the original developer of the R package ''cluster'' along with Mia Hubert and Anja Struyf. The Rousseeuw-Croux scale estimator Q_n is an efficient alternative to the
median absolute deviation In statistics, the median absolute deviation (MAD) is a robust measure of the variability of a univariate sample of quantitative data. It can also refer to the population parameter that is estimated by the MAD calculated from a sample. For a un ...
(see robust measures of scale). With Ida Ruts and
John Tukey John Wilder Tukey (; June 16, 1915 – July 26, 2000) was an American mathematician and statistician, best known for the development of the fast Fourier Transform (FFT) algorithm and box plot. The Tukey range test, the Tukey lambda distributi ...
he introduced the bagplot, a bivariate generalization of the boxplot. His more recent work has focused on concepts and algorithms for statistical depth functions in the settings of multivariate, regression and functional data, and on robust
principal component analysis Principal component analysis (PCA) is a popular technique for analyzing large datasets containing a high number of dimensions/features per observation, increasing the interpretability of data while preserving the maximum amount of information, and ...
. His current research is on visualization of classification and cellwise outliers.


Recognition

Rousseeuw was elected Member of
International Statistical Institute The International Statistical Institute (ISI) is a professional association of statisticians. It was founded in 1885, although there had been international statistical congresses since 1853. The institute has about 4,000 elected members from gov ...
(1991), Fellow of
Institute of Mathematical Statistics The Institute of Mathematical Statistics is an international professional and scholarly society devoted to the development, dissemination, and application of statistics and probability. The Institute currently has about 4,000 members in all parts o ...
(1993), and Fellow of the
American Statistical Association The American Statistical Association (ASA) is the main professional organization for statisticians and related professionals in the United States. It was founded in Boston, Massachusetts on November 27, 1839, and is the second oldest continuousl ...
(1994). His 1984 paper on robust regression has been reprinted in ''Breakthroughs in Statistics'', which collected and annotated the 60 most influential papers in statistics from 1850 to 1990. He became an
ISI highly cited researcher The Institute for Scientific Information (ISI) was an academic publishing service, founded by Eugene Garfield in Philadelphia in 1956. ISI offered scientometric and bibliographic database services. Its specialty was citation indexing and analysis, ...
in 2003, and was awarded the Jack Youden Prize (2019) and the Frank Wilcoxon Prize (2022).


Creation of the Rousseeuw Prize for Statistics

From 2016 onward Peter Rousseeuw worked on creating a new biennial prize, sponsored by him. The goal of the prize is to recognize outstanding statistical innovations with impact on society, and to promote awareness of the important role and intellectual content of statistics and its profound impact on human endeavors. The award amount is 1 million US dollars, similar to the Nobel Prize in other fields. The first award in 2022 went to the topic of Causal Inference in Medicine and Public Health. It was presented by His Majesty King
Philippe of Belgium french: Philippe Léopold Louis Mariegerman: Philipp Leopold Ludwig Maria , house = Belgium , father = Albert II of Belgium , mother = Paola Ruffo di Calabria , birth_date = , birth_place = Belvédère Castle, Laeken, B ...
to the laureates
James Robins James M. Robins is an epidemiologist and biostatistician best known for advancing methods for drawing causal inferences from complex observational studies and randomized trials, particularly those in which the treatment varies with time. He is ...
, Andrea Rotnitzky, Thomas Richardson, Miguel Hernán and Eric Tchetgen Tchetgen.


References

{{DEFAULTSORT:Rousseeuw, Peter Living people 1956 births Belgian statisticians People from Wilrijk Fellows of the American Statistical Association Fellows of the Institute of Mathematical Statistics R (programming language) people