[R] Testing autocorrelation & heteroskedasticity of residuals in ts

[Pfaff, Bernhard]

> 
> Hi,
> 
> I'm dealing with time series. I usually use stl() to
> estimate trend, stagionality and residuals. I test for
> normality of residuals using shapiro.test(), but I
> can't test for autocorrelation and heteroskedasticity.
> Is there a way to perform Durbin-Watson test and
> Breusch-Pagan test (or other simalar tests) for time
> series?
> I find dwtest() and bptest() in the package lmtest,

Hello Vito,

how about:

library(lmtest)
data(nottem)
test <- summary(stl(nottem, s.win=4))
bptest(formula(nottem ~ -1 + test$time.series[,1] + test$time.series[,2]))
dwtest(formula(nottem ~ -1 + test$time.series[,1] + test$time.series[,2]))

i.e. you define the residuals by providing the residuals as formula. 
Note:
testres <- nottem-test$time.series[,1]-test$time.series[,2]
cbind(testres, test$time.series[,3])

Anyway, are these tests applicable to stl as far as the underlying
assumptions for the error term is concerned?

Bernhard


> but it requieres an lm object, while I've a ts object.
> Any help will be appreciated.
> Best
> Vito
> 
> =====
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> 
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