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Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts Assessment Program National Center for Atmospheric Research 28 August 2017 Environmental Risk Modeling and Extreme Events Workshop 28 – 31 August 2017 Centre de Recherches Mathématiques, Montréal, Québec, Canada

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Page 1: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

Extreme value analysis with the R package extRemes

Eric GillelandResearch Applications Laboratory

Weather and Climate Impacts Assessment ProgramNational Center for Atmospheric Research

28 August 2017

Environmental Risk Modeling and Extreme Events Workshop28 – 31 August 2017

Centre de Recherches Mathématiques, Montréal, Québec, Canada

Page 2: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

Background Information• Software funded by the Weather and Climate Impacts

Assessment Science Program (http://www.assessment.ucar.edu)

• Project impetus, and continuing involvement, from Rick Katz (http://www.isse.ucar.edu/staff/katz)

• Primary goal is to shorten learning curve for atmospheric scientists to apply extreme value analysis (EVA) in their work when appropriate

• Two R (http://www.r-project.org) packages: extRemes(command-line) and in2extRemes (GUI for some extRemes functions)

• Web page for extRemes and in2extRemes (http://www.ral.ucar.edu/staff/ericg/extRemes)

Page 3: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

Background InformationTutorials for extRemes and in2extRemes• Gilleland, E. and R. W. Katz, 2016. extRemes

2.0: An Extreme Value Analysis Package in R. Journal of Statistical Software, 72 (8), 1 - 39, DOI: 10.18637/jss.v072.i08 (https://www.jstatsoft.org/article/view/v072i08).

• Gilleland, E. and Katz, R. W., 2016: in2extremes: Into the R Package extremes - Extreme Value Analysis for Weather and Climate Applications. NCAR Technical Note, NCAR/TN-523+STR, 102 pp., DOI: 10.5065/D65T3HP2 (http://dx.doi.org/10.5065/D65T3HP2).

Page 4: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

Background InformationOther EVA software (not just R packages, but mostly):• List of EVA software at

http://www.ral.ucar.edu/staff/ericg/softextreme.php• Gilleland, E., 2016. Computing Software. Chapter 25 In Extreme

Value Modeling and Risk Analysis: Methods and Applications. Edts. Dipak K. Dey and Jun Yan, CRC Press, Boca Raton, Florida, U.S.A., pp. 505 - 515.

• Gilleland, E. and Ribatet, M., 2015. Reinsurance and extremal events. In: Computational Actuarial Science with R. Ed. A. Charpentier, Chapman & Hall/CRC the R series, Boca Raton, Florida, U.S.A., pp. 257 - 286.

• Gilleland, E., M. Ribatet and A. G. Stephenson, 2013. A software review for extreme value analysis. Extremes, 16 (1), 103 - 119, DOI: 10.1007/s10687-012-0155-0 (available online at http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/s10687-012-0155-0).

• Stephenson, A. and E. Gilleland, 2005. Software for the Analysis of Extreme Events: The Current State and Future Directions. Extremes, 8, 87 - 109.

Page 5: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

fevd

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

Main function for all (univariate) extreme value distribution (EVD) fitting

fevd(x, data, threshold = NULL, threshold.fun = ~1, location.fun = ~1, scale.fun = ~1, shape.fun = ~1, use.phi = FALSE, type = c("GEV", "GP", "PP",

"Gumbel", "Exponential"),method = c("MLE", "GMLE", "Bayesian", "Lmoments"), initial = NULL, span, units = NULL, time.units = "days", period.basis = "year",na.action = na.fail, optim.args = NULL, priorFun = NULL, priorParams = NULL, proposalFun = NULL, proposalParams = NULL,iter = 9999, weights = 1, blocks = NULL, verbose = FALSE)

It’s not as bad as it looks!

Page 6: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

fevd

Zmax <- matrix( rnorm( 100 * 1000 ), 1000, 100 )

dim( Zmax )

Zmax <- apply( Zmax, 2, max )

dim( Zmax )

Fit GEV to block maxima using MLE

Samples of size 100 of maxima of standard normal distributed samples

Page 7: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

library( extRemes )

fit <- fevd( Zmax )

fit

fevdFit GEV to block maxima using MLE

Load the library

Do the fit

See a summary of the fit

Page 8: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

plot( fit )

ci( fit, type = “parameter” )

distill( fit )

strip( fit )

fevdFit GEV to block maxima using MLE

Look at diagnostic plots for the fit

Obtain CI’s for the GEV parameters

See just the parameter estimates and some other information (useful for multiple fits, e.g., thousands of locations)

New (not yet available). Same as distill(), but simpler (only parameter estimates shown)

Page 9: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

data( SEPTsp )

?SEPTsp

Maximum winter temperature (oC) in Sept-Iles, Québec

fevdFit GEV to block maxima using MLE

Page 10: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

1950 1960 1970 1980 1990

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Maximum winter temperature (oC) in Sept-Iles, Québec

fevdFit GEV to block maxima using MLE

Page 11: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

fit0 <- fevd(TMX1, data = SEPTsp, units = "deg C")

fit0

Maximum winter temperature (oC) in Sept-Iles, Québec

fevdFit GEV to block maxima using MLE

Page 12: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

fit0

fevd(x = TMX1, data = SEPTsp, units = "deg C")

[1] "Estimation Method used: MLE" Negative Log-Likelihood Value: 134.9045

Estimated parameters: location scale shape

18.1978488 3.1266252 -0.1395647

Standard Error Estimates: location scale shape

0.4999587 0.3616231 0.1168080

Estimated parameter covariance matrix. location scale shape

location 0.24995872 0.04741458 -0.02468781scale 0.04741458 0.13077124 -0.02121723shape -0.02468781 -0.02121723 0.01364411

AIC = 275.8091

BIC = 281.6045

Maximum winter temperature (oC) in Sept-Iles, Québec

fevdFit GEV to block maxima using MLE

Page 13: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

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fevd(x = TMX1, data = SEPTsp, units = "deg C")

Maximum winter temperature (oC) in Sept-Iles, Québec

fevdFit GEV to block maxima using MLE

plot( fit0 )

Page 14: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

ci( fit0, type = "parameter” )fevd(x = TMX1, data = SEPTsp, units = "deg C")

[1] "Normal Approx." 95% lower CI Estimate 95% upper CI

location 17.2179478 18.1978488 19.17774993scale 2.4178570 3.1266252 3.83539336shape -0.3685042 -0.1395647 0.08937479

ci( fit0 )fevd(x = TMX1, data = SEPTsp, units = "deg C")

[1] "Normal Approx.”

[1] "100-year return level: 28.812”

[1] "95% Confidence Interval: (24.7221, 32.9011)"

Maximum winter temperature (oC) in Sept-Iles, Québec

fevdFit GEV to block maxima using MLE

Page 15: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

fit1 <- fevd( TMX1, data = SEPTsp, location.fun = ~AOindex, units = "deg C")

fit1Negative Log-Likelihood Value: 134.4556 Estimated parameters: mu0 mu1 scale shape 18.1781844 -0.4220587 3.0397157 -0.1043810 Standard Error Estimates: mu0 mu1 scale shape 0.4853334 0.4388729 0.3527318 0.1177925 …AIC = 276.9112 BIC = 284.6385

Maximum winter temperature (oC) in Sept-Iles, Québec

fevdFit GEV to block maxima using MLE

Results shortened for space

Recall for fit0 thatAIC = 275.8091 BIC = 281.6045 Indicating fit0 is better!

µ(AOindex) = µ0 + µ1 * AOindex

Page 16: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

plot(fit1)

Maximum winter temperature (oC) in Sept-Iles, Québec

fevdFit GEV to block maxima using MLE

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fevd(x = TMX1, data = SEPTsp, location.fun = ~AOindex, units = "deg C")

Page 17: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

lr.test(fit0, fit1)

Likelihood-ratio Test

data: TMX1TMX1

Likelihood-ratio = 0.89789, chi-square critical value = 3.8415, alpha =0.0500, Degrees of Freedom = 1.0000, p-value = 0.3433alternative hypothesis: greater

Maximum winter temperature (oC) in Sept-Iles, Québec

fevdFit GEV to block maxima using MLE

Result agrees with AIC and BIC

Page 18: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

(Negative) Minimum winter temperature (oC) in Sept-Iles, Québec

fevdFit GEV to minimum winter temperature (oC) using MLE

fit0 <- fevd(-TMN0 ~ 1, data = SEPTsp, units = “neg. deg. C”)

Page 19: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

fevdFort Collins, Colorado daily precipitation (inches) 1900 to 1999

Page 20: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

fevdFort Collins, Colorado daily precipitation (inches) 1900 to 1999

fit <- fevd( Prec, data = Fort, threshold = 0.395, type = "GP", units = "inches” )

Fit a GP distribution to the data

Page 21: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

fevdFort Collins, Colorado daily precipitation (inches) 1900 to 1999

plot( fit )

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●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●

●●●●●●●●●

●●●

● ● ●

fevd(x = Prec, data = Fort, threshold = 0.395, type = "GP", units = "inches", verbose = TRUE)

Fit a GP distribution to the data

Page 22: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

fevdFort Collins, Colorado daily precipitation (inches) 1900 to 1999

plot( fit, type = “trace” )

0.29 0.31 0.33 0.35

8586

8788

89

Neg

ative

Log−L

ikelih

ood

0.15 0.20 0.25

8586

8788

890.29 0.31 0.33 0.35

−200

010

020

0

scale

Neg

ative

Log−L

ikelih

ood

Gra

dien

t

0.15 0.20 0.25−1

00−5

00

50

shape

fevd(x = Prec, data = Fort, threshold = 0.395, type = "GP", units = "inches", verbose = TRUE)

Page 23: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

fevdFort Collins, Colorado daily precipitation (inches) 1900 to 1999

fit <- fevd( Prec, Fort, threshold = 0.395, type = "PP", units = "inches” )

Fit a Poisson Point Process to the data

Page 24: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

fevdFort Collins, Colorado daily precipitation (inches) 1900 to 1999plot( fit )

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●

●●●●●●●

●●●●●●

●● ● ●

● ●●

1 2 3 4 5

12

34

Model Quantiles

Empi

rical

Qua

ntile

s

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●

●●●● ● ●

● ● ●●●●●

●●●● ● ●

1 2 3 4

12

34

Prec( > 0.395) Empirical Quantiles

Qua

ntile

s fro

m M

odel

Sim

ulat

ed D

ata

1−1 lineregression line95% confidence bands

0 1 2 3 4 5

0.0

0.2

0.4

0.6

N = 100 Bandwidth = 0.2654

Dens

ity

Empirical (year maxima)Modeled

0 2 4 6

02

46

810

Z plot

Expected ValuesUnder exponential(1)

Obs

erve

d Z_

k Va

lues

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●

●●●●●●●

●●●●●●●

●●

●●

●●

1−1 lineregression line95% confidence bands

2 5 10 20 50 100 500

24

68

12

Return Levels based on approx.equivalent GEV

Return Period (years)

Retu

rn L

evel

(inc

hes)

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

●●●●●●●●●●●●

●● ● ●● ● ●

fevd(x = Prec, data = Fort, threshold = 0.395, type = "PP", units = "inches", verbose = TRUE)

See Smith, R. L. and Shively, T. S., 1995. A point process approach to modeling trends in tropospheric ozone. Atmospheric Environment, 29, 3489 – 3499.

Also: http://www.stat.unc.edu/postscript/rs/var.pdf

Page 25: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

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fevdEstimated economic damage (billions USD) caused by hurricanes

●●●●●●●●

●●●● ● ●

● ●

10 15 20 25 30 35

1030

5070

Model Quantiles

Empi

rical

Qua

ntile

s

●●●●●●●●●●●

●●● ●●

10 20 30 40 50 60 70

2060

100

140

Dam( > 6) Empirical Quantiles

Qua

ntile

s fro

m M

odel

Sim

ulat

ed D

ata

1−1 lineregression line95% confidence bands

0 20 40 60

0.00

0.05

0.10

0.15

N = 18 Bandwidth = 2.289

Den

sity

EmpiricalModeled

2 5 10 50 200 500

−100

100

300

Return Period (years)

Ret

urn

Leve

l

●●●●●●●●●●●●●●● ●●

fevd(x = Dam, data = damage, threshold = 6, type = "GP", time.units = "2.05/year")

Data not taken every x time units, so must estimate an average number of events per year.

Page 26: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

Threshold SelectionPlot parameter estimates over a range of thresholds

● ● ● ● ● ● ● ●

0.2 0.4 0.6 0.8

−2.0

−0.5

0.5

1.5

threshrange.plot(x = Denversp$Prec, r = c(0.1, 0.95))

repa

ram

eter

ized

scal

e

●●

● ● ● ● ● ●

0.2 0.4 0.6 0.8

−1.0

0.0

1.0

2.0

Threshold

shap

eGeneralized Pareto

Range of thresholds

Page 27: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

UCAR Confidential and Proprietary. © 2017, University Corporation for Atmospheric Research. All rights reserved.

Threshold Selection

●● ●

●● ●

●●

●●

● ●

●●

105 106 107 108 109 110

115.0

116.0

threshrange.plot(x = Tphap$MaxT, r = c(105, 110), type = "PP", nint = 20)

location

●●

●●

●●

●●

105 106 107 108 109 110

0.8

1.2

1.6

scale

●●

●●

105 106 107 108 109 110

−0.4

−0.2

0.0

Threshold

shape

Plot parameter estimates over a range of thresholds

Poisson Point Process

Specify type = “PP”

Change number of thresholds over the specified range

Page 28: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

Declustering

UCAR Confidential and Proprietary. © 2014, University Corporation for Atmospheric Research. All rights reserved.

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50 60 70 80 90

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110

Year

Sky Harbor airport, Phoenix, Arizona July to August maximum temperatures ( oF)

Page 29: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

Declustering

UCAR Confidential and Proprietary. © 2014, University Corporation for Atmospheric Research. All rights reserved.

threshrange.plot(Tphap$MaxT, r = c(105, 110), type = "PP")

Sky Harbor airport, Phoenix, Arizona July to August maximum temperatures ( oF)

●● ●

●● ●

●●

●●

● ●

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105 106 107 108 109 110

115.0

116.0

threshrange.plot(x = Tphap$MaxT, r = c(105, 110), type = "PP", nint = 20)

location

●●

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105 106 107 108 109 110

0.8

1.2

1.6

scale

●●

●●

105 106 107 108 109 110

−0.4

−0.2

0.0

Threshold

shape

Page 30: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

Declustering

UCAR Confidential and Proprietary. © 2014, University Corporation for Atmospheric Research. All rights reserved.

extremalindex( Tphap$MaxT, threshold = 105 )

θ Number of Clusters

Run Length

0.21 234 2

Sky Harbor airport, Phoenix, Arizona July to August maximum temperatures ( oF)

Page 31: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

Declustering

UCAR Confidential and Proprietary. © 2014, University Corporation for Atmospheric Research. All rights reserved.

y <- decluster( Tphap$MaxT, threshold = 105, r = 2 )

y

plot( y )

Sky Harbor airport, Phoenix, Arizona July to August maximum temperatures ( oF)

Page 32: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

Declustering

UCAR Confidential and Proprietary. © 2014, University Corporation for Atmospheric Research. All rights reserved.

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0 500 1000 1500 2000 2500

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decluster.runs(x = Tphap$MaxT, threshold = 105, r = 2)

index

Tphap$MaxT

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Sky Harbor airport, Phoenix, Arizona July to August maximum temperatures ( oF)

Page 33: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

Declustering

UCAR Confidential and Proprietary. © 2014, University Corporation for Atmospheric Research. All rights reserved.

Sky Harbor airport, Phoenix, Arizona July to August maximum temperatures ( oF)

θ Number of Clusters

Run Length

1 229 3

extremalindex( y, threshold = 105 )

Page 34: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

Declustering

UCAR Confidential and Proprietary. © 2014, University Corporation for Atmospheric Research. All rights reserved.

Tphap2 <- TphapTphap2$MaxT.dc <- c(y)

fit <- fevd( MaxT.dc, threshold = 105, data = Tphap2, type = "PP",time.units = "62/year", units = "deg F” )

Sky Harbor airport, Phoenix, Arizona July to August maximum temperatures ( oF)

Page 35: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

Declustering

UCAR Confidential and Proprietary. © 2014, University Corporation for Atmospheric Research. All rights reserved.

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●

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● ●

106 108 110 112 114 116 118

106

110

114

118

Model Quantiles

Empi

rical

Qua

ntile

s

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106 108 110 112 114 116 118

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118

MaxT.dc( > 105) Empirical Quantiles

Qua

ntile

s fro

m M

odel

Sim

ulat

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ata

1−1 lineregression line95% confidence bands

105 110 115 120

0.00

0.10

N = 43 Bandwidth = 0.9037

Dens

ity

Empirical (year maxima)Modeled

0 1 2 3 4 5 6

12

34

5

Z plot

Expected ValuesUnder exponential(1)

Obs

erve

d Z_

k Va

lues

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1−1 lineregression line95% confidence bands

2 5 10 20 50 100 500

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Return Levels based on approx.equivalent GEV

Return Period (years)

Retu

rn L

evel

(deg

F)

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fevd(x = MaxT.dc, data = Tphap2, threshold = 105, type = "PP", units = "deg F", time.units = "62/year")Sky Harbor airport, Phoenix, Arizona July to August maximum temperatures ( oF)

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Tail dependence

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Reiss, R.-D. and Thomas, M., 2007. Statistical Analysis of Extreme Values: with applications to insurance, finance, hydrology and other fields. Birkhäuser, 530pp., 3rd edition.

z <- runif( 100, -1, 0 ) w <- -1*(1 + z) taildep( z, w, u = 0.8 )taildep.test( z, w )

Example where a random variable is completely dependent in terms of the variables, but completely tail independent (from Reiss and Thomas (2007) p. 75.

Page 37: Extreme value analysis with the R package extRemes · Extreme value analysis with the R package extRemes Eric Gilleland Research Applications Laboratory Weather and Climate Impacts

Future Plans• New bootstrap options (testing stage)

§ Currently only parametric bootstrap with percentile method is available via ci() function

§ Multiple options for regular bootstrap using the distillery package

• m < n bootstrap• iid and block bootstrap options• Multiple choices for estimated intervals (e.g., BCa, basic,

bootstrap-t, normal, etc.)§ Test-inversion bootstrap also using distillery package

• New bivariate EVA functionality (with help from Dan Cooley; early stage)

• Other … (thinking stage; funding dependent)

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Discussion Questions• What functionality is missing from the

software that would be most useful to include (that is not already on the docket)?

• Open-source software, such as extRemes, is use-at-your-own-risk. But, is a proprietary package better?

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Thanks! Questions?

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