将关键图例添加到 R 中的多直方图

Question

如何在下图中添加关键图例

我希望在右上角的某处有一个关键图例，带有两个短的水平彩条，红色的应该说“整形手术出错”，蓝色的应该说“德国”。

我使用以下代码来制作情节：

bar2 <- read.table("div/ana-mut[...]/barriers-set-2.dat", sep=" ")
bar2val <- c(bar2$V1, bar2$V2)
bar3 <- read.table("div/ana-mut[...]/barriers-set-3.dat", sep=" ")
bar3val <- c(bar3$V1, bar3$V2)
p1 <- hist(subset(bar2val, bar2val < 30), breaks=30)
p2 <- hist(subset(bar3val, bar3val < 30), breaks=30)
plot(p1, col=rgb(1,0,0,8/9), main="Barrier distribution", xlab="Barrier [kcal/mol]", ylab="Mutant count")
plot(p2, col=rgb(0,0,1,8/9), add=T)

任何提示将不胜感激。

Answer 1

这是另一种解决方案（请参阅下面的代码）

# some semi-random data …
df <- structure(list(Germany = c(1L, 3L, 6L, 1L, 2L), Plastic = c(2L, 
5L, 4L, 2L, 3L)), .Names = c("Germany", "Plastic"), class = "data.frame", row.names = c(NA, 
-5L))

# Expand right side of clipping rect to make room for the legend
par(xpd=T, mar=par()$mar+c(0,0,0,4))

# Graph data (transposing the matrix) using heat colors,  
# put 10% of the space between each bar, and make labels  
# smaller with horizontal y-axis labels
barplot(t(df), main="Barrier distribution", xlab="Barrier [kcal/mol]", ylab="Mutant count", 
   col=c("blue", "red"), space=0.1, cex.axis=0.8, las=1,
   names.arg=c("Mon","Tue","Wed","Thu","Fri"), cex=0.8) 

# Place the legend at (4,9) using blue and red
legend(4, 9, names(df), lwd=4, col=c("blue", "red"))

# Restore default clipping rect
par(mar=c(5, 4, 4, 2) + 0.1)

Answer 2

legend 命令可以解决问题：

legend("topright", c("Germany", "Plastic"), col=c("blue", "red"), lwd=10)

要获得两个短的水平彩条，只需使用标准线，但增加线条粗细。正如 Roland 指出的，您还可以使用 fill 参数：

legend("topright", c("Germany", "Plastic"), fill=c("blue", "red"))

更多详情请见?legend。