xlab坐标里面有中文
encoding="GB2312"也不行。
pdf(file = ifelse(onefile, "Rplots.pdf", "Rplot%03d.pdf"),
width, height, onefile, family, title, fonts, version,
paper, encoding, bg, fg, pointsize, pagecentre, colormodel,
useDingbats, useKerning, fillOddEven, compress)