1、 predict reg gnp96 L.gnp96 predict gnp_hat6)清除时间标识: tsset, clear1.2变量的生成与处理1)滞后项、超前项和差分项 help tsvarlist gen Lgnp = L.gnp96 /*一阶滞后*/ gen L2gnp = L2.gnp96 gen Fgnp = F.gnp96/*一阶超前*/ gen F2gnp = F2.gnp96 gen Dgnp = D.gnp96 /*一阶差分*/ gen D2gnp = D2.gnp96 list in 1/102)产生增长率变量: 对数差分 gen lngnp = ln(gnp96)
2、gen growth = D.lngnp gen growth2 = (gnp96-L.gnp96)/L.gnp96 gen diff = growth - growth2 /*表明对数差分和变量的增长率差别很小*/ list date gnp96 lngnp growth* diff in 1/101.3日期的处理日期的格式 help tsfmt基本时点:整数数值,如 -3, -2, -1, 0, 1, 2, 3 .1960年1月1日,取值为 0;显示格式:定义含义默认格式%td日%tdDlCY%tw周%twCY!ww%tm月%tmCY!mn%tq季度%tqCY!qq%th半年%thCY!h
3、h%ty年%tyCY1)使用 tsset 命令指定显示格式 use B6_tsset.dta, clear tsset t, daily list tsset t, weekly list 2)指定起始时点 cap drop month generate month = m(1990-1) + _n - 1 format month %tm list t month in 1/20 cap drop year gen year = y(1952) + _n - 1 format year %ty list t year in 1/203)自己设定不同的显示格式日期的显示格式 %d (%td)
4、定义如下:%-td具体项目释义:“ F = . Residual | .02521709 122 .000206697 R-squared = 0.0000-+- Adj R-squared = 0.0000 Total | .02521709 122 .000206697 Root MSE = .01438- D.ln_wpi | Coef. Std. Err. t P|t| 95% Conf. Interval-+- _cons | .0108215 .0012963 8.35 0.000 .0082553 .0133878. estat archlm,lags(1)LM test for
5、 autoregressive conditional heteroskedasticity (ARCH)- lags(p) | chi2 df Prob chi2-+- 1 | 8.366 1 0.0038 H0: no ARCH effects vs. H1: ARCH(p) disturbance通过对wpi的对数差分进行常数回归,接着用LM检验来判断ARCH(1)效应,在该例子中,检验的结果Prob chi20.0038 chi2 = . | OPG D.ln_wpi | Coef. Std. Err. z P|z| 95% Conf. Intervalln_wpi | _cons |
6、 .0061167 .0010616 5.76 0.000 .0040361 .0081974ARCH | arch | L1. | .4364123 .2437428 1.79 0.073 -.0413147 .9141394 | garch | L1. | .4544606 .1866605 2.43 0.015 .0886126 .8203085 _cons | .0000269 .0000122 2.20 0.028 2.97e-06 .0000508这样,我们就可以估计出了ARCH(1)的系数是0.436,GARCH(1)的系数是0.454,所以我们可以拟合出GARCH(1,1)模型
7、:接下来我们可以对变量的进行预测:predict xb,xb /*对差分变量的预测*/predict variance,var /*对条件方差的预测 */predict res,residuals /*对差分变量残差的预测*/predict yres,yresiduals /*对未差分变量残差的预测*/3.2 ARCH模型的确定以及检验 *- 检验 ARCH 效应是否存在:archlm 命令 regress D.ln_wpi archlm, lag(1/20) regress D.ln_wpi L(1/3).D.ln_wpi * 图形法自相关函数图 (ac) reg D.ln_wpi predict e, res gen e2 = e2 ac e2, l
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