search for: upper95

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2011 May 22
1
How to calculate confidence interval of C statistic by rcorr.cens
...of logistic regression model using rcorr.cens in rms package. I wrote a brief function for this purpose as the followings; CstatisticCI <- function(x) # x is object of rcorr.cens. { se <- x["S.D."]/sqrt(x["n"]) Low95 <- x["C Index"] - 1.96*se Upper95 <- x["C Index"] + 1.96*se cbind(x["C Index"], Low95, Upper95) } Then, > MyModel.lrm.rcorr <- rcorr.cens(x=predict(MyModel.lrm), S=df$outcome) > MyModel.lrm.rcorr C Index Dxy S.D. n missing uncensored 0.8222785...
2011 Nov 20
1
Cox proportional hazards confidence intervals
...ventions. I can successfully obtain the LR, Wald, and Score test p-values from the coxph.object, as well as the hazard ratio as follows: formula.obj = Surv(days, status) ~ type coxph.model = coxph(formula.obj, df) fit = summary(coxph.model) hazard.ratio = fit$conf.int[1] lower95 = fit$conf.int[3] upper95 = fit$conf.int[4] logrank.p.value = fit$sctest[3] wald.p.value = fit$waldtest[3] lr.p.value = fit$logtest[3] I had intended to report logrank P values with the hazard ratio and CI obtained from this function. In one case the P was 0.04 yet the CI crossed one, which confused me, and certainly will...
2011 Jul 20
0
Cleveland Dot plots: tick labels and error bars
...ption I've observed is from: http://www.unc.edu/courses/2010fall/ecol/563/001/docs/solutions/assign2.htm It seems to use the following panel function to create 95% conf. intervals: panel=function(x,y) { panel.grid(v=0, h=-6, lty=3) panel.segments(new.data$lower95, as.numeric(y), new.data$upper95, as.numeric(y), lty=1, col=1) panel.segments(new.data$lower50, as.numeric(y), new.data$upper50, as.numeric(y), lty=1, lwd=4, col='grey60') panel.xyplot(x, y, pch=16, cex=1.2, col='white') panel.xyplot(x, y, pch=1, cex=1.1, col='black') panel.abline(v=0, col=2, lty=2) }...