Fits AR and subset AR models and provides complete model building capabilities. FitAR
For model estimation the main function is FitAR for which generic methods print, summary, coef, plot and predict are implemented. For model identification, there is a new PacfPlot for subset ARz idenfication. Subset models may also be selected using AIC, BIC and UBIC criteria with the function SelectModel. SelectModel produces a S3 class object, "SelectModel", for which their is a plot method. The main fitting function is FitAR. New methods and generic functions, BoxCox, Boot and sdfplot are given. Methods for print, summary, coef, residuals, fitted and predict implemented.
Package: | FitAR |
Type: | Package |
Version: | 1.93 |
Date: | 2013-03-15 |
License: | GPL (>= 2) |
LazyLoad: | yes |
LazyData: | yes |
To get started please see the documentation and examples given in the functions PacfPlot, SelectModel and FitAR.
R functions for model diagnostic checking, simulation and forecasting are also available. The function plot provides many graphical diagnostic plots.
Model Selection:
TimeSeriesPlot
,
PacfPlot
,
SelectModel
Model Checking:
plot.FitAR
,
BoxCox
,
LBQPlot
,
RacfPlot
,
JarqueBeraTest
,
Model Applications:
Boot
,
SimulateGaussianAR
A. I. McLeod and Ying Zhang
Maintainer: aimcleod@uwo.ca
McLeod, A.I. and Zhang, Y. (2006). Partial autocorrelation parameterization for subset autoregression. Journal of Time Series Analysis, 27, 599-612.
McLeod, A.I. and Zhang, Y. (2008a). Faster ARMA Maximum Likelihood Estimation, Computational Statistics and Data Analysis 52-4, 2166-2176. DOI link: http://dx.doi.org/10.1016/j.csda.2007.07.020.
McLeod, A.I. and Zhang, Y. (2008b). Improved Subset Autoregression: With R Package. Journal of Statistical Software.
Changjiang Xu and A. I. McLeod (2010). Bayesian information criterion with Bernoulli prior. Submitted for publication.
Changjiang Xu and A. I. McLeod (2010). Model selection using generalized information criterion. Submitted for publication.
#Scripts are given below for all Figures and Tables in McLeod and Zhang (2008b). # #Figure 1. Plot of lynx time series using plot.ts plot(lynx) #Figure 2. Plot of lynx series using TimeSeriesPlot TimeSeriesPlot(lynx, type="o", pch=16, ylab="# pelts", main="Lynx Trappings") #Figure 3. Trellis plot for Ninemile series graphics.off() #clear previous graphics data(Ninemile) print(TimeSeriesPlot(Ninemile, SubLength=200)) #Figure 4. Partial autocorrelation plot of lynx series graphics.off() #clear previous graphics PacfPlot(log(lynx)) ## Not run: #takes some time for all these examples #Figure 5. Using SelectModel to select the best subset ARz or ARp and # comparing BIC and UBIC subset selection. # graphics.off() #clear previous graphics layout(matrix(1:4,ncol=2),respect=TRUE) ansBICp<-SelectModel(log(lynx),lag.max=15,Criterion="BIC", ARModel="ARp", Best=3) ansUBICp<-SelectModel(log(lynx),lag.max=15, ARModel="ARp", Best=3) ansBICz<-SelectModel(log(lynx),lag.max=15,Criterion="BIC", ARModel="ARz", Best=3) ansUBICz<-SelectModel(log(lynx),lag.max=15, ARModel="ARz", Best=3) par(mfg=c(1,1)) plot(ansBICp) par(mfg=c(2,1)) plot(ansUBICp) par(mfg=c(1,2)) plot(ansBICz) par(mfg=c(2,2)) plot(ansUBICz) #Figure 6. Logged spectral density function fitted to square-root of monthly # sunspot series using the non-subset AR and subset ARz. # AIC and BIC are used for the AR while BIC and UBIC are used # for the ARz. Takes about 115 seconds on 3.6 GHz Pentium PC. graphics.off() #clear previous graphics layout(matrix(1:4,ncol=2),respect=TRUE) z<-sqrt(sunspots) P<-200 pAIC<-SelectModel(z, lag.max=P, ARModel="AR", Best=1, Criterion="AIC") ARAIC<-FitAR(z, pAIC) par(mfg=c(1,1)) sdfplot(ARAIC) title(main="AIC Order Selection") pBIC<-SelectModel(z, lag.max=P, ARModel="AR", Best=1, Criterion="BIC") ARBIC<-FitAR(z, pBIC) par(mfg=c(1,2)) sdfplot(ARBIC) title(main="BIC Order Selection") SunspotMonthARzBIC<-SelectModel(z,lag.max=P, ARModel="ARz", Best=1, Criterion="BIC") ARzBIC<-FitAR(z, SunspotMonthARzBIC) par(mfg=c(2,1)) sdfplot(ARzBIC) title(main="BIC Subset Selection") SunspotMonthARzUBIC<-SelectModel(z,lag.max=P, ARModel="ARz", Best=1) ARzUBIC<-FitAR(z, SunspotMonthARzUBIC) par(mfg=c(2,2)) sdfplot(ARzUBIC) title(main="UBIC Subset Selection") #Table 3. #First part of table: AR(1) and AR(2). #Only timings for GetFitAR and FitAR since the R function ar produces too many # warnings and an error message as noted in McLeod and Zhang (2008b, p.12). #The ar function with mle option is not recommended. start.time<-proc.time() set.seed(661177723) NREP<-100 #takes about 156 sec NREP<-10 #takes about 16 sec ns<-c(50,100,200,500,1000) ps<-c(1,2) #AR(p), p=1,2 tmsA<-matrix(numeric(4*length(ns)*length(ps)),ncol=4) ICOUNT<-0 for (IP in 1:length(ps)){ p<-ps[IP] for (ISIM in 1:length(ns)){ ICOUNT<-ICOUNT+1 n<-ns[ISIM] ptm <- proc.time() for (i in 1:NREP){ phi<-PacfToAR(runif(p, min=-1, max =1)) z<-SimulateGaussianAR(phi,n) phiHat<-try(GetFitAR(z,p,MeanValue=mean(z))$phiHat) } t1<-(proc.time() - ptm)[1] # ptm <- proc.time() for (i in 1:NREP){ phi<-PacfToAR(runif(p, min=-1, max =1)) z<-SimulateGaussianAR(phi,n) phiHat<-try(FitAR(z,p,MeanMLEQ=TRUE)$phiHat) } t2<-(proc.time() - ptm)[1] # ptm <- proc.time() for (i in 1:NREP){ phi<-PacfToAR(runif(p, min=-1, max =1)) z<-SimulateGaussianAR(phi,n) #uncomment this line and next two lines for ar timings -- expect lots of # warnings and an error message!! #phiHat<-try(ar(z,aic=FALSE,order.max=p,method="mle")$ar) #delete this line and the next one phiHat<-NA } #uncomment this line for ar timings #t3<-(proc.time() - ptm)[1] t3<-NA #delete this line for ar timings tmsA[ICOUNT,]<-c(n,t1,t2,t3) } } rnames<-c(rep("AR(1)", length(ns)),rep("AR(2)", length(ns)) ) cnames<-c("n", "GetFitAR", "FitAR", "ar") dimnames(tmsA)<-list(rnames,cnames) tmsA[,-1]<-round(tmsA[,-1]/NREP,2) end.time<-proc.time() total.time<-(end.time-start.time)[1] #Second part of table: AR(20) and AR(40). #NOTE: ar is not recommended with method="mle" produces numerous warnings # and also takes a long time! start.time<-proc.time() set.seed(661177723) NREP<-100 #takes 7.5 hours NREP<-10 #takes 45 minutes ns<-c(1000,2000,5000) ps<-c(20,40) tmsB<-matrix(numeric(4*length(ns)*length(ps)),ncol=4) ICOUNT<-0 for (IP in 1:length(ps)){ p<-ps[IP] phi<-PacfToAR(0.8/(1:p)) for (ISIM in 1:length(ns)){ ICOUNT<-ICOUNT+1 n<-ns[ISIM] ptm <- proc.time() for (i in 1:NREP){ z<-SimulateGaussianAR(phi,n) phiHat<-try(GetFitAR(z,p,MeanValue=mean(z))$phiHat) } t1<-(proc.time() - ptm)[1] ptm <- proc.time() for (i in 1:NREP){ z<-SimulateGaussianAR(phi,n) phiHat<-try(FitAR(z,p,MeanMLEQ=TRUE)$phiHat) } t2<-(proc.time() - ptm)[1] ptm <- proc.time() for (i in 1:NREP){ z<-SimulateGaussianAR(phi,n) phiHat<-try(ar(z,aic=FALSE,order.max=p,method="mle")$ar) } t3<-(proc.time() - ptm)[1] tmsB[ICOUNT,]<-c(n,t1,t2,t3) } } rnames<-c( rep("AR(20)", length(ns)), rep("AR(40)", length(ns)) ) cnames<-c("n", "GetFitAR", "FitAR", "ar") dimnames(tmsB)<-list(rnames,cnames) tmsB[,-1] <- round(tmsB[,-1]/NREP,2) end.time<-proc.time() total.time<-(end.time-start.time)[1] #Figure 7. Comparing Box-Cox analyses using FitAR and MASS library(MASS) graphics.off() #clear previous graphics layout(matrix(c(1,2,1,2),ncol=2)) pvec<-c(1,2,4,10,11) out<-FitAR(lynx, ARModel="ARp", pvec) BoxCox(out) PMAX<-max(pvec) Xy <- embed(lynx, PMAX + 1) y <- Xy[, 1] X <- (Xy[, -1])[, pvec] #pvec != 1 outlm<-lm(y~X) boxcox(outlm,lambda=seq(0.0,0.6,0.05)) #Figure 8 graphics.off() #clear previous graphics BoxCox(AirPassengers) #takes about 30 sec #Figure 9 graphics.off() #clear previous graphics data(rivers) BoxCox(rivers) title(sub="Length of 141 North American Rivers") #Figure 10 graphics.off() #clear previous graphics data(USTobacco) TimeSeriesPlot(USTobacco, aspect=1) #Figure 11 graphics.off() #clear previous graphics data(USTobacco) outUST<-arima(USTobacco, c(0,1,1)) BoxCox(outUST) #Figure 12. Basic diagnostic plots for ARp fitted to the log lynx series graphics.off() #clear previous graphics out<-FitAR(log(lynx), ARModel="ARp", c(1,2,4,10,11)) plot(out, terse=TRUE) #Figure 13. RSF plot for ARp fitted to log lynx series graphics.off() #clear previous graphics out<-FitAR(log(lynx), ARModel="ARp", c(1,2,4,10,11)) rfs(out) #Table 6. Comparison of bootstrap and large-sample sd #Use bootstrap to compute standard errors of parameters #takes about 34 seconds on a 3.6 GHz PC ptm <- proc.time() #user time set.seed(2491781) #for reproducibility R<-100 #number of bootstrap iterations p<-c(1,2,4,7,10,11) ans<-FitAR(log(lynx),p) out<-Boot(ans, R) fn<-function(z) FitAR(z,p)$zetaHat sdBoot<-sqrt(diag(var(t(apply(out,fn,MARGIN=2))))) sdLargeSample<-coef(ans)[,2][1:6] sd<-matrix(c(sdBoot,sdLargeSample),ncol=2) dimnames(sd)<-list(names(sdLargeSample),c("Bootstrap","LargeSample")) ptm<-(proc.time()-ptm)[1] sd ## End(Not run)
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