x=1:92
y1<-read.table("C:/Users/Administrator/Desktop/5555.txt")
y2<-read.table("C:/Users/Administrator/Desktop/6666.txt")
plot(x,y1,xlab="指数",ylab="EWMA值",col="blue",pch=16,lty=1,type="o",xlim=c(1,92),ylim=c(-1.5,2))
lines(x,y2,col="red",pch=17,lty=1,type="o",xlim=c(1,92),ylim=c(-1.5,2))
U<-0.710
C<--0.013
L<--0.737
abline(h=U,lty=3,lwd=1)
abline(h=C,lty=3,lwd=1)
abline(h=L,lty=3,lwd=1)
axis(4,at = c(0.710,-0.013,-0.737),labels = c("U","C","L"),las=1,tick=0)
title("ZH-2值和均价的EWMA控制图对比")

如题，求教大神，怎么把图像里标题，x，y轴的标题里的字母换成New Roman字体，而文字还是小四宋体呢？