File: plot_estimate_gev_fremantle.py

package info (click to toggle)
openturns 1.24-4
  • links: PTS, VCS
  • area: main
  • in suites: forky, sid, trixie
  • size: 66,204 kB
  • sloc: cpp: 256,662; python: 63,381; ansic: 4,414; javascript: 406; sh: 180; xml: 164; yacc: 123; makefile: 98; lex: 55
file content (666 lines) | stat: -rw-r--r-- 26,081 bytes parent folder | download | duplicates (2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
"""
Estimate a GEV on the Fremantle sea-levels data
===============================================
"""

# %%
# In this example, we illustrate various techniques of extreme value modeling applied
# to the annual maximum sea-levels recorded at Fremantle, near Perth, western Australia, over the period
# 1897-1989.
# Readers should refer to [coles2001]_ to get more details.
#
# We illustrate techniques to:
#
# - estimate a stationary and a non stationary GEV depending on time or on the covariates (time, SOI),
# - estimate a return level,
#
# using:
#
# - the log-likelihood function,
# - the profile log-likelihood function.
#
# We also illustrate the modelling with covariates.
#
# First, we load the Fremantle dataset of the annual maximum sea-levels. We start by looking at them
# through time. The data also contain the annual mean value of the Southern Oscillation Index (SOI),
# which is a proxy for meteorological volatility due to effects such as El Nino.
import openturns as ot
import openturns.viewer as otv
from openturns.usecases import coles

data = coles.Coles().fremantle
print(data[:5])
graph = ot.Graph(
    "Annual maximum sea-levels at Fremantle", "year", "level (m)", True, ""
)
cloud = ot.Cloud(data[:, :2])
cloud.setColor("red")
graph.add(cloud)
graph.setIntegerXTick(True)
view = otv.View(graph)

# %%
# We select the sea-levels column.
sample = data[:, 1]

# %%
# **Stationary GEV modeling via the log-likelihood function**
#
# We first assume that the dependence through time is negligible, so we first model the data as
# independent observations over the observation period. We estimate the parameters of the
# GEV distribution by maximizing the log-likelihood of the data.
factory = ot.GeneralizedExtremeValueFactory()
result_LL = factory.buildMethodOfLikelihoodMaximizationEstimator(sample)

# %%
# We get the fitted GEV and its parameters :math:`(\hat{\mu}, \hat{\sigma}, \hat{\xi})`.
fitted_GEV = result_LL.getDistribution()
desc = fitted_GEV.getParameterDescription()
param = fitted_GEV.getParameter()
print(", ".join([f"{p}: {value:.3f}" for p, value in zip(desc, param)]))

# %%
# We get the asymptotic distribution of the estimator :math:`(\hat{\mu}, \hat{\sigma}, \hat{\xi})`.
# In that case, the asymptotic distribution is normal.
parameterEstimate = result_LL.getParameterDistribution()
print("Asymptotic distribution of the estimator : ")
print(parameterEstimate)

# %%
# We get the covariance matrix  and the standard deviation of :math:`(\hat{\mu}, \hat{\sigma}, \hat{\xi})`.
print("Cov matrix = \n", parameterEstimate.getCovariance())
print("Standard dev = ", parameterEstimate.getStandardDeviation())

# %%
# We get the marginal confidence intervals of order 0.95.
order = 0.95
for i in range(3):
    ci = parameterEstimate.getMarginal(i).computeBilateralConfidenceInterval(order)
    print(desc[i] + ":", ci)

# %%
# At last, we can validate the inference result thanks the 4 usual diagnostic plots:
#
# - the probability-probability pot,
# - the quantile-quantile pot,
# - the return level plot,
# - the empirical distribution function.
validation = ot.GeneralizedExtremeValueValidation(result_LL, sample)
graph = validation.drawDiagnosticPlot()
view = otv.View(graph)

# %%
# **Stationary GEV modeling via the profile log-likelihood function**
#
# Now, we use the profile log-likehood function rather than log-likehood function  to estimate the parameters of the GEV.
result_PLL = factory.buildMethodOfXiProfileLikelihoodEstimator(sample)

# %%
# The following graph allows one to get the profile log-likelihood plot.
# It also indicates the optimal value of :math:`\xi`, the maximum profile log-likelihood and
# the confidence interval for :math:`\xi` of order 0.95 (which is the default value).
order = 0.95
result_PLL.setConfidenceLevel(order)
view = otv.View(result_PLL.drawProfileLikelihoodFunction())

# %%
# We can get the numerical values of the confidence interval: it appears to be a bit smaller
# than the interval obtained with the log-likelihood function.
# Note that if the order requested is too high, the confidence interval might not be calculated because
# one of its bound is out of the definition domain of the log-likelihood function.
try:
    print("Confidence interval for xi = ", result_PLL.getParameterConfidenceInterval())
except Exception as ex:
    print(type(ex))
    pass

# %%
# **Return level estimate from the estimated stationary GEV**
#
# We estimate the :math:`m`-block return level :math:`z_m`: it is computed as a particular quantile of the
# GEV model estimated using the log-likelihood function. We just have to use the maximum log-likelihood
# estimator built in the previous section.
#
# As the data are annual sea-levels, each block corresponds to one year: the 10-year return level
# corresponds to :math:`m=10` and the 100-year return level corresponds to :math:`m=100`.
#
# The method provides the asymptotic distribution of the estimator :math:`\hat{z}_m`
# which mean is the return-level estimate.
zm_10 = factory.buildReturnLevelEstimator(result_LL, 10.0)
return_level_10 = zm_10.getMean()
print("Maximum log-likelihood function : ")
print(f"10-year return level = {return_level_10}")
return_level_ci10 = zm_10.computeBilateralConfidenceInterval(0.95)
print(f"CI = {return_level_ci10}")

# %%
zm_100 = factory.buildReturnLevelEstimator(result_LL, 100.0)
return_level_100 = zm_100.getMean()
print(f"100-year return level = {return_level_100}")
return_level_ci100 = zm_100.computeBilateralConfidenceInterval(0.95)
print(f"CI = {return_level_ci100}")

# %%
# **Return level estimate via the profile log-likelihood function of a stationary GEV**
#
# We can estimate the :math:`m`-block return level :math:`z_m` directly from the data using the profile
# likelihood with respect to :math:`z_m`.
result_zm_10_PLL = factory.buildReturnLevelProfileLikelihoodEstimator(sample, 10.0)
zm_10_PLL = result_zm_10_PLL.getParameter()
print(f"10-year return level (profile) = {zm_10_PLL}")

# %%
# We can get the confidence interval of :math:`z_m`:  once more, it appears to be a bit smaller
# than the interval obtained from the log-likelihood function.
# As for the confidence interval of :math:`\xi`, depending on the order requested, the interval might
# not be calculated.
result_zm_10_PLL.setConfidenceLevel(0.95)
try:
    return_level_ci10 = result_zm_10_PLL.getParameterConfidenceInterval()
except Exception as ex:
    print(type(ex))
    pass
print("Maximum profile log-likelihood function : ")
print(f"CI={return_level_ci10}")

# %%
# We can also plot the profile log-likelihood function and get the confidence interval, the optimal value
# of :math:`z_m` and its confidence interval.
view = otv.View(result_zm_10_PLL.drawProfileLikelihoodFunction())

# %%
# **Non stationary GEV modeling via the log-likelihood function**
#
# If we look at the data carefully, we see that the pattern of variation has not remained constant over
# the observation period. There is an increase in the data through time.
# We want to model this dependence because a slight increase in extreme sea-levels might have
# a significant impact on the safety of coastal flood defenses.
#
# We have define the functional basis for each parameter of the GEV model. Even if we have
# the possibility to affect a time-varying model to each of the 3 parameters :math:`(\mu, \sigma, \xi)`,
# it is strongly recommended not to vary the parameter :math:`\xi` and to let it constant.
#
# For numerical reasons, it is strongly recommended to normalize all the data as follows:
#
# .. math::
#
#     \tau(t) = \dfrac{t-c}{d}
#
# where:
#
# - the *CenterReduce* method where :math:`c = \dfrac{1}{n} \sum_{i=1}^n t_i` is the mean time stamps
#   and :math:`d = \sqrt{\dfrac{1}{n} \sum_{i=1}^n (t_i-c)^2}` is the standard deviation of the time stamps;
# - the *MinMax* method where :math:`c = t_1` is the initial time and :math:`d = t_n-t_1` the final time;
# - the *None* method where :math:`c = 0` and :math:`d = 1`: in that case, data are not normalized.
#
# We suppose that :math:`\mu` is linear in time, and that the other parameters remain constant:
#
# .. math::
#     :nowrap:
#
#     \begin{align*}
#       \mu(t) & = \beta_1 + \beta_2\tau(t) \\
#       \sigma(t) & = \beta_3 \\
#       \xi(t) & = \beta_4
#     \end{align*}
#
constant = ot.SymbolicFunction(["t"], ["1.0"])
basis = ot.Basis([constant, ot.SymbolicFunction(["t"], ["t"])])
# basis for mu, sigma, xi
muIndices = [0, 1]  # linear
sigmaIndices = [0]  # stationary
xiIndices = [0]  # stationary

# %% We need to get the time stamps (in years here).
timeStamps = data[:, 0]

# %%
# We can now estimate the list of coefficients :math:`\vect{\beta} = (\beta_1, \beta_2, \beta_3, \beta_4)`
# using the log-likelihood of the data.
#
# We test the 3 normalizing methods and both initial points in order to evaluate their impact on the results.
# We can see that:
#
# - both normalization methods lead to the same result for :math:`\beta_1`, :math:`\beta_3` and :math:`\beta_4`
#   (note that :math:`\beta_2` depends on the normalization function),
# - both initial points lead to the same result when the data have been normalized,
# - it is very important to normalize all the data: if not, the result strongly depends on the initial point
#   and it differs from the result obtained with normalized data. The results are not optimal in that case
#   since the associated log-likelihood are much smaller than those obtained with normalized data.
#
print("Linear mu(t) model:")
for normMeth in ["MinMax", "CenterReduce", "None"]:
    for initPoint in ["Gumbel", "Static"]:
        print(f"normMeth = {normMeth}, initPoint = {initPoint}")
        # The ot.Function() is the identity function.
        result = factory.buildTimeVarying(
            sample,
            timeStamps,
            basis,
            muIndices,
            sigmaIndices,
            xiIndices,
            ot.Function(),
            ot.Function(),
            ot.Function(),
            initPoint,
            normMeth,
        )
        beta = result.getOptimalParameter()
        print(f"beta = {beta}")
        print(f"Max log-likelihood = {result.getLogLikelihood()}")

# %%
# According to the previous results, we choose the *MinMax* normalization method and the *Gumbel* initial point.
# This initial point is cheaper than the *Static* one as it requires no optimization computation.
result_NonStatLL = factory.buildTimeVarying(
    sample,
    timeStamps,
    basis,
    muIndices,
    sigmaIndices,
    xiIndices,
    ot.Function(),
    ot.Function(),
    ot.Function(),
    "Gumbel",
    "MinMax",
)
beta = result_NonStatLL.getOptimalParameter()
print(f"beta = {beta}")
print(f"mu(t) = {beta[0]:.4f} + {beta[1]:.4f} * tau(t)")
print(f"sigma = {beta[2]:.4f}")
print(f"xi = {beta[3]:.4f}")

# %%
# You can get the expression of the normalizing function :math:`t \mapsto \tau(t)`:
normFunc = result_NonStatLL.getNormalizationFunction()
print("Function tau(t): ", normFunc)
print("c = ", normFunc.getEvaluation().getImplementation().getCenter()[0])
print("1/d = ", normFunc.getEvaluation().getImplementation().getLinear()[0, 0])

# %%
# You can get the function :math:`t \mapsto \vect{\theta}(t)` where :math:`\vect{\theta}(t) = (\mu(t), \sigma(t), \xi(t))`.
functionTheta = result_NonStatLL.getParameterFunction()

# %%
# We get the asymptotic distribution of :math:`\vect{\beta}` to compute some confidence intervals of
# the estimates, for example of order :math:`p = 0.95`.
dist_beta = result_NonStatLL.getParameterDistribution()
confidence_level = 0.95
for i in range(beta.getSize()):
    lower_bound = dist_beta.getMarginal(i).computeQuantile((1 - confidence_level) / 2)[
        0
    ]
    upper_bound = dist_beta.getMarginal(i).computeQuantile((1 + confidence_level) / 2)[
        0
    ]
    print(
        "Conf interval for beta_"
        + str(i + 1)
        + " = ["
        + str(lower_bound)
        + "; "
        + str(upper_bound)
        + "]"
    )

# %%
# In order to compare different modelings, we get the optimal log-likelihood of the data for both stationary
# and non stationary models. The difference is significant enough to be in favor of the non stationary model.
print("Max log-likelihood: ")
print("Stationary model =  ", result_LL.getLogLikelihood())
print("Non stationary linear mu(t) model =  ", result_NonStatLL.getLogLikelihood())

# %%
# In order to draw some diagnostic plots similar to those drawn in the stationary case, we refer to the
# following result: if :math:`Z_t` is a non stationary GEV model parametrized by :math:`(\mu(t), \sigma(t), \xi(t))`,
# then the standardized variables :math:`\hat{Z}_t` defined by:
#
# .. math::
#
#    \hat{Z}_t = \dfrac{1}{\xi(t)} \log \left[1+ \xi(t)\left( \dfrac{Z_t-\mu(t)}{\sigma(t)} \right)\right]
#
# have  the standard Gumbel distribution which is the GEV model with :math:`(\mu, \sigma, \xi) = (0, 1, 0)`.
#
# As a result, we can validate the inference result thanks the 4 usual diagnostic plots:
#
# - the probability-probability pot,
# - the quantile-quantile pot,
# - the return level plot,
# - the data histogram and the density of the fitted model.
#
# using the transformed data compared to the Gumbel model. We can see that the adequation is better
# than with the stationary model.
graph = result_NonStatLL.drawDiagnosticPlot()
view = otv.View(graph)

# %%
# We can draw the mean function  :math:`t \mapsto \Expect{\mbox{GEV}(t)}`. Be careful, it is not the function
# :math:`t \mapsto \mu(t)`. As a matter of fact, the mean is defined for :math:`\xi <1` only and in that case,
# for :math:`\xi \neq 0`, we have:
#
# .. math::
#     \Expect{\mbox{GEV}(t)} = \mu(t) + \dfrac{\sigma(t)}{\xi(t)} (\Gamma(1-\xi(t))-1)
#
# and for :math:`\xi = 0`, we have:
#
# .. math::
#     \Expect{\mbox{GEV}(t)} = \mu(t) + \sigma(t)\gamma
#
# where :math:`\gamma` is the Euler constant.
#
# We can also draw the function :math:`t \mapsto q_p(t)` where :math:`q_p(t)` is the quantile of
# order :math:`p` of the GEV distribution at time :math:`t`.
# Here, :math:`\mu(t)` is a linear function and the other parameters are constant, so the mean and the quantile
# functions are also linear functions.
graph = ot.Graph(
    r"Annual maximum sea-levels at Fremantle - Linear $\mu(t)$",
    "year",
    "level (m)",
    True,
    "",
)
graph.setIntegerXTick(True)
# data
cloud = ot.Cloud(data[:, :2])
cloud.setColor("red")
graph.add(cloud)
# mean function
meandata = [
    result_NonStatLL.getDistribution(t).getMean()[0] for t in data[:, 0].asPoint()
]
curve_meanPoints = ot.Curve(data[:, 0].asPoint(), meandata)
graph.add(curve_meanPoints)
# quantile function
graphQuantile = result_NonStatLL.drawQuantileFunction(0.95)
drawQuant = graphQuantile.getDrawable(0)
drawQuant = graphQuantile.getDrawable(0)
drawQuant.setLineStyle("dashed")
graph.add(drawQuant)
graph.setLegends(["data", "mean function", "quantile 0.95  function"])
graph.setLegendPosition("lower right")
view = otv.View(graph)


# %%
# At last, we can test the validity of the stationary model :math:`\mathcal{M}_0`
# relative to the model with time varying parameters  :math:`\mathcal{M}_1`. The
# model :math:`\mathcal{M}_0` is parametrized by :math:`(\beta_1, \beta_3, \beta_4)` and the model
# :math:`\mathcal{M}_1` is parametrized by :math:`(\beta_1, \beta_2, \beta_3, \beta_4)`: so we have
# :math:`\mathcal{M}_0 \subset \mathcal{M}_1`.
#
# We use the Likelihood Ratio test. The null hypothesis is the stationary model :math:`\mathcal{M}_0`.
# The Type I error :math:`\alpha` is taken equal to 0.05.
#
# This test confirms that the dependence through time is not negligible: it means that the linear :math:`\mu(t)`
# component explains a large variation in the data.
llh_LL = result_LL.getLogLikelihood()
llh_NonStatLL = result_NonStatLL.getLogLikelihood()
modelM0_Nb_param = 3
modelM1_Nb_param = 4
resultLikRatioTest = ot.HypothesisTest.LikelihoodRatioTest(
    modelM0_Nb_param, llh_LL, modelM1_Nb_param, llh_NonStatLL, 0.05
)
accepted = resultLikRatioTest.getBinaryQualityMeasure()
print(
    f"Hypothesis H0 (stationary model) vs H1 (linear mu(t) model):  accepted ? = {accepted}"
)

# %%
# We detail the statistics of the Likelihood Ratio test: the deviance statistics :math:`\mathcal{D}_p` follows
# a :math:`\chi^2_1` distribution.
# The model :math:`\mathcal{M}_0` is rejected if the deviance statistics estimated on the data is greater than
# the threshold :math:`c_{\alpha}` or if the p-value is less than the Type I error  :math:`\alpha = 0.05`.
print(f"Dp={resultLikRatioTest.getStatistic():.2f}")
print(f"alpha={resultLikRatioTest.getThreshold():.2f}")
print(f"p-value={resultLikRatioTest.getPValue():.2f}")

# %%
# We can perform the same study with a quadratic model for :math:`\mu(t)` or a linear model for
# :math:`\mu(t)` and :math:`\sigma(t)`:
#
# .. math::
#     :nowrap:
#
#     \begin{align*}
#       \mu(t) & = \beta_1 + \beta_2 \tau(t) + \beta_3\tau(t)^2 \\
#       \sigma(t) & = \beta_4 \\
#       \xi(t) & = \beta_5
#     \end{align*}
#
# or
#
# .. math::
#     :nowrap:
#
#     \begin{align*}
#     \mu(t) & = \beta_1 + \beta_2 \tau(t) \\
#     \sigma(t) & = \beta_3 + \beta_4\tau(t)\\
#     \xi(t) & = \beta_5
#     \end{align*}
#
# For each model, we give the log-likelihood values and we test the validity of each model with respect
# to the non stationary model where :math:`\mu(t)` is linear.
# We notice that there is no evidence to adopt a quadratic model for :math:`\mu(t)` nor a linear model
# for :math:`\mu(t)` and :math:`\sigma(t)`: the optimal log-likelihood for each model is very near the likelihood
# we obtained with a linear model for :math:`\mu(t)` only. It means that these both models do not bring significant
# improvements with respect to model tested before.
basis = ot.Basis(
    [constant, ot.SymbolicFunction(["t"], ["t"]), ot.SymbolicFunction(["t"], ["t^2"])]
)
result_NonStatLL_2 = factory.buildTimeVarying(
    sample,
    timeStamps,
    basis,
    [0, 1, 2],
    [0],
    [0],
    ot.Function(),
    ot.Function(),
    ot.Function(),
    "Gumbel",
    "MinMax",
)
result_NonStatLL_3 = factory.buildTimeVarying(
    sample,
    timeStamps,
    basis,
    [0, 1],
    [0, 1],
    [0],
    ot.Function(),
    ot.Function(),
    ot.Function(),
    "Gumbel",
    "MinMax",
)
print("Max log-likelihood = ")
print("Non stationary quadratic mu(t) model = ", result_NonStatLL_2.getLogLikelihood())
print(
    "Non stationary linear mu(t) and sigma(t) model = ",
    result_NonStatLL_3.getLogLikelihood(),
)
llh_LL = result_LL.getLogLikelihood()
llh_NonStatLL_2 = result_NonStatLL_2.getLogLikelihood()
llh_NonStatLL_3 = result_NonStatLL_3.getLogLikelihood()
resultLikRatioTest_2 = ot.HypothesisTest.LikelihoodRatioTest(
    4, llh_NonStatLL, 5, llh_NonStatLL_2, 0.05
)
resultLikRatioTest_3 = ot.HypothesisTest.LikelihoodRatioTest(
    4, llh_NonStatLL, 5, llh_NonStatLL_3, 0.05
)
accepted_2 = resultLikRatioTest_2.getBinaryQualityMeasure()
accepted_3 = resultLikRatioTest_3.getBinaryQualityMeasure()
print(
    f"Hypothesis H0 (linear mu(t) model) vs H1 (quadratic mu(t) model):  accepted ? = {accepted_2}"
)
print(
    f"Hypothesis H0 (linear mu(t) model) vs H1 (linear mu(t) and sigma(t) model):  accepted ? = {accepted_3}"
)

# %%
# **Non stationary GEV modeling with the covariates Time and SOI**
#
# Extreme sea-levels can be unusually extreme during periods when the El Nino effect is
# active.
# Hence, we study a modeling that takes into account the dependence between the extreme
# sea-levels
# at Fremantle and the annual mean value of the Southern Oscillation Index (SOI)
# besides the temporal dependence.
# The following figure shows that the annual maximum sea-levels are generally greater
# when the value of SOI is high. It might be due to the time trend in the data for the
# sea-levels
# and the SOI (each one increases with time). But it can also be possible that the
# SOI explains
# some of the variation in annual maximum sea-levels after allowance for the time variation
# in the process.
graph = ot.Graph("SOI at Fremantle", "SOI", "level (m)", True, "")
cloud = ot.Cloud(data.getMarginal([2, 1]))
cloud.setColor("red")
graph.add(cloud)
view = otv.View(graph)

# %%
# To consider this possibility, we study the model:
#
# .. math::
#     :nowrap:
#
#     \begin{align*}
#       \mu(t) & = \beta_1 t + \beta_2 \mbox{SOI} + \beta_3 \\
#       \sigma(t) & = \beta_4 \\
#       \xi(t) & = \beta_5
#     \end{align*}
#
# We consider two covariates: the time and the SOI. We build the sample of the values of both
# covariates: :math:`(t_i, \mbox{SOI}_i)_{1 \leq i \leq n}` where :math:`\mbox{SOI}_i =
# SOI(t_i)`.
# The constant covariate is
# automatically added by the library if not specified in order to allow
# some of the GEV parameters to remain constant (ie independent of both covariates
# :math:`(t, \mbox{SOI})`):
# this is the case for the :math:`\sigma` and :math:`\xi` parameters.
# This last constant covariate is associated to the
# third component of the covariates sample which now gathers the values
# :math:`(t_i, \mbox{SOI}_i, 1)` for :math:`1 \leq i \leq n`.
dataCovariates = data.getMarginal([0, 2])
print(dataCovariates[0:10])
result_Cov = factory.buildCovariates(sample, dataCovariates, [0, 1])

# %%
# We check here that a third component has effectively been added to the covariates
# sample: see the added third column which is constant equal to 1.
print(result_Cov.getCovariates()[0:10])

# %%
# We get the optimal parameter :math:`\vect{\beta}`.
beta = result_Cov.getOptimalParameter()
print("beta = ", beta)

# %%
# We get here the function :math:`(\vect{\beta}, t, \mbox{SOI}) \mapsto \vect{\theta}
# (\vect{\beta}, t, \mbox{SOI})` where :math:`\vect{\theta} = (\mu, \sigma, \xi)`. We see that
# :math:`\mu` depends on the three
# covariates :math:`(t, \mbox{SOI}, 1)` and that :math:`\sigma` and :math:`\xi` depends
# only on the third one
# which is the constant one.
print(result_Cov.getParameterFunction())
print(f"beta = {beta}")
print(f"mu(t) = {beta[0]:.4f} *t + {beta[1]:.4f} * SOI(t) + {beta[2]:.4f}")
print(f"sigma = {beta[3]:.4f}")
print(f"xi = {beta[4]:.4f}")

# %%
# We check here the normalizing function that has been used, which comes from
# the default method (the *MinMax* one).
print(result_Cov.getNormalizationFunction())

# %%
# We test this new model where :math:`\mu(t,SOI)` is modeled as a linear combination
# of the three covariates  :math:`(t, \mbox{SOI}, 1)` against the model
# with the linear-trend only :math:`\mu(t)`. The maximized log-likelihood of this
# new model is 53.9, compared to 49.9 for the first model. Hence, the
# deviance statistics is equal to :math:`D = 8.0`, which is large when judged relative to
# a :math:`\chi_1^2` distribution.
# It provides evidence that the effect of SOI is influential on annual maximum
# sea-levels at Fremantle, even after the allowance for time-variation.
llh_cov = result_Cov.getLogLikelihood()
print("Max log-likelihood: ", llh_cov)
resultLikRatioTest_SOI = ot.HypothesisTest.LikelihoodRatioTest(
    4, llh_NonStatLL, 5, llh_cov, 0.05
)
print(f"Dp={resultLikRatioTest_SOI.getStatistic():.2f}")
accepted = resultLikRatioTest_SOI.getBinaryQualityMeasure()
print(
    f"Hypothesis H0 (linear-trend mu(t) model) vs H1 (linear-trend and SOI mu(t,SOI) model):  accepted ? = {accepted}"
)

# %%
# We plot here the graphs :math:`t \mapsto \mu(t, \mbox{SOI}_0)` where
# :math:`\mbox{SOI}_0` is a given value (the mean value of the sample if not specified),
# and :math:`\mbox{SOI} \mapsto \mu(t_0, \mbox{SOI})` where :math:`t_0` is a given time.
# Care: there are three covariates :math:`(t, SOI, 1)` for the reasons mentioned previously.
# Then the reference point must be of dimension 3.
#
# As the relation is linear (the link function is the Identity function), we get some straight
# lines.
# The third graph is the dependence on the third covariate which is constant.
refSOI = dataCovariates.computeMean()[1]
refTime = 1940
refPoint = [refTime, refSOI, 1]
gridMu = result_Cov.drawParameterFunction1D(0, refPoint)
view = otv.View(gridMu)

# %%
# To adapt the labels and get rid of the last graph:
graphCol = gridMu.getGraphCollection()
graphMu1 = graphCol[0]
graphMu1.setTitle(r"$t \mapsto \mu(t, SOI_0)$, $SOI_0$ = {0:.2f}".format(refSOI))
graphMu1.setXTitle("t")
graphMu2 = graphCol[1]
graphMu2.setTitle(r"$SOI \mapsto \mu(t_0, SOI)$, $t_0 = $" + str(refTime))
graphMu2.setXTitle("SOI")
newGridLayout = ot.GridLayout(1, 2)
newGridLayout.setGraph(0, 0, graphMu1)
newGridLayout.setGraph(0, 1, graphMu2)
view = otv.View(newGridLayout)

# %%
# We plot here the graph :math:`(t, SOI) \mapsto \mu(t, SOI)`.
# As the third covariate is constant, the other graphs :math:`(t, 1)
# \mapsto \mu(t, \mbox{SOI}_0, 1)`
# and :math:`(1, SOI) \mapsto \mu(t_0, 1, SOI)` are not interesting
# as we have already obtained them with the previous method.
graphCol = result_Cov.drawParameterFunction2D(0, refPoint)
view = otv.View(graphCol)

# %%
# We plot here the graphs :math:`t \mapsto q_p(Z_{t, \mbox{SOI}_0})`
# and :math:`\mbox{SOI} \mapsto q_p(Z_{t_0, \mbox{SOI}})` where :math:`Z_{t, \mbox{SOI}_0}`
# is the process whose excesses of :math:`u` follow the estimated GPD,
# depending on the covariates :math:`(t, SOI)`. Then :math:`q_p`
# is the quantile of order :math:`p`.
# Because of the constant third covariate, the last graph is reduced to a point.
p = 0.95
gridQuantile = result_Cov.drawQuantileFunction1D(p, refPoint)
view = otv.View(gridQuantile)

# %%
# To adapt the labels and get rid of the last graph:
graphCol = gridQuantile.getGraphCollection()
graphQuant1 = graphCol[0]
graphQuant1.setTitle(r"$t \mapsto q_p(Z(t, SOI_0))$, $SOI_0$ = {0:.2f}".format(refSOI))
graphQuant1.setXTitle("t")
graphQuant1.setYTitle(r"$q_p$")
graphQuant2 = graphCol[1]
graphQuant2.setTitle(r"$SOI \mapsto q_p(Z(t_0, SOI))$, $t_0 = $" + str(refTime))
graphQuant2.setXTitle("SOI")
graphQuant2.setYTitle(r"$q_p$")
newGridLayout = ot.GridLayout(1, 2)
newGridLayout.setGraph(0, 0, graphQuant1)
newGridLayout.setGraph(0, 1, graphQuant2)
view = otv.View(newGridLayout)

# %%
otv.View.ShowAll()