abstract
A recentseriesofpapersbyCharlesT.Perrettiandcollaboratorshaveshownthatnonparametric
forecasting methodscanoutperformparametricmethodsinnoisynonlinearsystems.Suchasituation
can arisebecauseoftwomainreasons:theinstabilityofparametricinferenceproceduresinchaotic
systemswhichcanleadtobiasedparameterestimates,andthediscrepancybetweentherealsystem
dynamics andthemodeledone,aproblemthatPerrettiandcollaboratorscall “the truemodelmyth”.
Should ecologistsgoonusingthedemandingparametricmachinerywhentryingtoforecastthe
dynamics ofcomplexecosystems?Orshouldtheyrelyontheelegantnonparametricapproachthat
appears sopromising?Itwillbeherearguedthatecologicalforecastingbasedonparametricmodels
presents twokeycomparativeadvantagesovernonparametricapproaches.First,thelikelihoodof
parametric forecastingfailurecanbediagnosedthankstosimpleBayesianmodelcheckingprocedures.
Second, whenparametricforecastingisdiagnosedtobereliable,forecastinguncertaintycanbe
estimated onvirtualdatageneratedwiththe fitted todataparametricmodel.Incontrast,nonparametric
techniquesprovideforecastswithunknownreliability.Thisargumentationisillustratedwiththesimple
theta-logistic modelthatwaspreviouslyusedbyPerrettiandcollaboratorstomaketheirpoint.Itshould
convince ecologiststosticktostandardparametricapproaches,untilmethodshavebeendevelopedto
assess thereliabilityofnonparametricforecasting
บทคัดย่อRecentseriesofpapersbyCharlesT.Perrettiandcollaboratorshaveshownthatnonparametric การคาดการณ์ methodscanoutperformparametricmethodsinnoisynonlinearsystems Suchasituationสามารถ arisebecauseoftwomainreasons:theinstabilityofparametricinferenceproceduresinchaoticsystemswhichcanleadtobiasedparameterestimates, andthediscrepancybetweentherealsystemandthemodeledone dynamics, aproblemthatPerrettiandcollaboratorscall "truemodelmyth"ควร ecologistsgoonusingthedemandingparametricmachinerywhentryingtoforecastthedynamics ofcomplexecosystems Orshouldtheyrelyontheelegantnonparametricapproachthatปรากฏ sopromising Itwillbeherearguedthatecologicalforecastingbasedonparametricmodelsนำเสนอ twokeycomparativeadvantagesovernonparametricapproaches แรก thelikelihoodofforecastingfailurecanbediagnosedthankstosimpleBayesianmodelcheckingprocedures พาราเมตริก2, whenparametricforecastingisdiagnosedtobereliable, forecastinguncertaintycanbeประมาณ onvirtualdatageneratedwiththe ติดตั้ง todataparametricmodel Incontrast, nonparametrictechniquesprovideforecastswithunknownreliability Thisargumentationisillustratedwiththesimpleทีตาโลจิสติก modelthatwaspreviouslyusedbyPerrettiandcollaboratorstomaketheirpoint.Itshouldมั่นใจ ecologiststosticktostandardparametricapproaches, untilmethodshavebeendevelopedtoประเมิน thereliabilityofnonparametricforecasting
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