R语言绘制森林图报错，求指导！

rt=read.table("uniCox.xls",header=T,sep="\t",row.names=1,check.names=F)

data=as.matrix(rt)

HR=data[,1:3]

hr=sprintf("%.3f",HR[,"HR"])

hrLow=sprintf("%.3f",HR[,"HR.95L"])

hrHigh=sprintf("%.3f",HR[,"HR.95H"])

pVal=data[,"pvalue"]

pVal=ifelse(pVal<0.001, "<0.001", sprintf("%.3f", pVal))

tabletext <- 

 list(c(NA, rownames(HR)),

    append("pvalue", pVal),

    append("Hazard ratio",paste0(hr,"(",hrLow,"-",hrHigh,")")) )      

pdf(file="forest.pdf",

    width = 60,       

    height = 40,       

    )

forestplot(tabletext, 

      rbind(rep(NA, 3), HR),

      col=clrs,

      graphwidth=unit(200, "mm"),

      xlog=T,

      lwd.ci=2,

      boxsize=1.6,

      xlab="Hazard ratio"

      )

dev.off()

然后报错显示：

Error in valid.viewport(x, y, width, height, just, gp, clip, xscale, yscale, : 

 invalid 'xscale' in viewport

请问哪里出了错，需要怎么调整？谢谢！