我想通过两个变量预测肿瘤恶性阳性和阴性，我的数据大概是这样的，样本量67个，阳性的有20个，redscore是连续自变量，PNEP是分类变量，PNEP不显著。这是我的R代码

library(survival)

 library(rms)

 ddist <- datadist(a)

 options(datadist='ddist')

 logistic.lrm <- lrm(outcome~Radscore+PNEP,data=a,x=T,y=T,maxit=1000)

 nomogram <- nomogram(logistic.lrm,fun=plogis,fun.at = c(0,0.05,seq(0.1,0.9,by=0.1),0.95,1))

 plot(nomogram)

call <- calibrate(logistic.lrm,method = "boot",B=1000)

 plot(call,xlim = c(0,1.0),ylim = c(0,1.0))