各位大神,想问下Cox回归中设定了分层变量(level=2),也就是说会将数据按照不同的两层进行拟合,coxph()得出的其他变量的参数应该有两套啊,为什么只有一套呢?代码和输出结果如下:
>cox1<-coxph(Surv(days,status==1)~log(thick)+sex+strata(ulc))#这是模型,包含了一个分层变量ulc;
> summary(cox1) Call:coxph(formula = Surv(days, status == 1) ~ log(thick) + sex + strata(ulc)) n= 205, number of events= 57 coef exp(coef) se(coef) z Pr(>|z|) log(thick) 0.5599 1.7505 0.1784 3.139 0.0017 **sex 0.3600 1.4333 0.2702 1.332 0.1828 #sex和log(thick)的系数估计值只一个,是针对哪一层的呢---Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 exp(coef) exp(-coef) lower .95 upper .95log(thick) 1.750 0.5713 1.234 2.483sex 1.433 0.6977 0.844 2.434Concordance= 0.673 (se = 0.058 )Rsquare= 0.063 (max possible= 0.9 )Likelihood ratio test= 13.3 on 2 df, p=0.001296Wald test = 12.88 on 2 df, p=0.001598Score (logrank) test = 12.98 on 2 df, p=0.00152


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