将x轴标签直接放在R中的条形图中的刻度标记下

Question

我有一张表（下图）显示了小组实验中存在的树种（分类变量）的百分比。我的目标是绘制y轴上树种的百分比和物种＆＃39;在条形图中的x轴上。

问题

我的问题是我遇到了正确格式化x轴的问题。我的目标是确保**＆＃39; Species＆＃39; **的x轴标签是： -

1. 直接位于其标记下方的刻度线
2. 不要重叠到绘图区域

如果有人可以帮助解决这个问题，我将非常感激。



R代码

  df <- leaf.percent[order(leaf.percent$Leaf.Percentge, decreasing = TRUE),]

  Tree.labels<-c("Quercus robar", "Quercus Patraea",
                 "Deciduous", "Oak",
                 "Plant", "Shrub")

  par(mar=c(6, 6, 3, 3))

  Tree<-barplot(df$Leaf.Percentge, names.arg = df$Species,
                xaxt = "n",
                ylab="Percentage %", 
                xlab="Tree Species",
                col="lightblue",
                ylim = c(0, 60))

    axis(1, at=Tree, labels=FALSE)

    text(seq(1, 6, by=1), par("usr")[3] - 0.2, 
         labels=unique(Tree.labels), 
         srt = 25, pos = 1, 
         xpd = TRUE, cex=0.7)

数据

structure(list(Species = structure(1:6, .Label = c("Deciduous", 
"Oak", "Plant", "Quercus_petraea", "Quercus_robur", "Shrub"), class =     "factor"), 
Frequency = c(48L, 29L, 6L, 70L, 206L, 4L), Leaf.Percentge =     c(13.2231404958678, 
7.98898071625344, 1.65289256198347, 19.2837465564738, 56.7493112947658, 
1.10192837465565)), .Names = c("Species", "Frequency", "Leaf.Percentge"
), row.names = c(NA, -6L), class = "data.frame")