我想添加标题,“1999年至2008年美国PM2.5的排放”,该标题使用r中的基本绘图功能。在那,我希望2.5成为PM的下标。如果PM2.5恰好位于字符串的末尾,我没有任何问题:
barplot(height = total.emissions$Emissions, names.arg=total.emissions$year,
xlab="Year", ylab= " Amount of emitted in tonsPM"2.5 ,
main = "Emissions from in the United States from 1999 to 2008PM"[2.5] )
但如果它位于字符串的中间,我就不能这样做。如果我把它分成两部分,如下:
barplot(height = total.emissions$Emissions, names.arg=total.emissions$year,
xlab="Year", ylab= " Amount of PM_[2.5] emitted in tons",
main = expression("Emissions from PM"[2.5] "in the United States from 1999 to 2008"))
由于方括号,我收到错误说明意外符号。
答案 0 :(得分:10)
尝试paste
的{{1}}功能(详见expression
),例如:
?plotmath