epoh,向你请教:
我在用R包中自带的数据进行门限回归学习;发现有些问题要向请教。
> library(TSA)
> data(prey.eq)
> prey.tar.1=tar(y=log(prey.eq),p1=4,p2=4,d=3,a=.1,b=.9,print=TRUE)
time series included in this analysis is: log(prey.eq)
SETAR(2, 1 , 4 ) model delay = 3
estimated threshold = 4.661 from a Minimum AIC fit with thresholds
searched from the 17 percentile to the 81 percentile of all data.
The estimated threshold is the 56.6 percentile of
all data.
lower regime:
Residual Standard Error=0.2341
R-Square=0.9978
F-statistic (df=2, 28)=6355.76
p-value=0
Estimate Std.Err t-value Pr(>|t|)
intercept-log(prey.eq) 0.2621 0.3156 0.8305 0.4133
lag1-log(prey.eq) 1.0175 0.0704 14.4455 0.0000
(unbiased) RMS
0.05479
with no of data falling in the regime being
log(prey.eq) 30
(max. likelihood) RMS for each series (denominator=sample size in the regime)
log(prey.eq) 0.05114
upper regime:
Residual Standard Error=0.2676
R-Square=0.9971
F-statistic (df=5, 18)=1253.556
p-value=0
Estimate Std.Err t-value Pr(>|t|)
intercept-log(prey.eq) 4.1986 1.2841 3.2697 0.0043
lag1-log(prey.eq) 0.7081 0.2023 3.5005 0.0026
lag2-log(prey.eq) -0.3009 0.3118 -0.9648
0.3474
lag3-log(prey.eq) 0.2788 0.4063 0.6861
0.5014
lag4-log(prey.eq) -0.6113 0.2726 -2.2427
0.0377
(unbiased) RMS
0.07158
with no of data falling in the regime being
23
(max. likelihood) RMS for each series (denominator=sample size in the regime)
0.05602
Nominal AIC is 10.92
我的问题是,在高区中的滞后2,3,4项的回归系数在一定的显著水平下,P值不算好。那么我肯定要在滞后2,3,4中进行选择最好的。比如,我首先选择lag3-log的系数为零,进行回归,再来看结果。
请回:1、在门限回归中要不要对各区的系数进行显著性或不显著性判定(用其P值)。
2、如果应当这样作的话,那么我们又如何来限制不显著的系数为零呢?请就这个结果和prey.tar.1=tar(y=log(prey.eq),p1=4,p2=4,d=3,a=.1,b=.9,print=TRUE)语句邦助修改。谢谢!
3、另外我试了一种限制的办法,也是不行的。
prey.tar.1=tar(y=log(prey.eq),p1=4,p2=4,fixed=c(NA,Na,0,Na,NA),d=3,a=.1,b=.9,print=TRUE)
错误于tar(y = log(prey.eq), p1 = 4, p2 = 4, fixed = c(NA,Na,0,Na,NA), :
参数((fixed = c(NA,Na,0,Na,NA))) 没有用。