如何使用2列制作R图例？

Question

我想在我的图表上制作一个图例，该图例由plot()函数生成。原始legend()函数将生成一个只有1列的列表。如何制作包含2列的图例？

Answer 1

我无法通过一次调用legend标准图来找到方法。

这是一个选项，绘制两个单独的图例：一个带有线和点，一个带有标签。 x.intersp可用于调整标签和线条之间的距离。

plot(cumsum(runif(n = 100)))

# draw legend with lines and point but without labels and box. x.intersp controls horizontal distance between lines
L = legend(x = 'bottom', legend = rep(NA,4), col=1:2, lty=c(1,1,2,2), ncol=2, bty='n', x.intersp=0.5, pch=c(1,2,1,2), inset=0.02)

# use position data of previous legend to draw legend with invisble lines and points but with labels and box. x.intersp controls distance between lines and labels
legend(x = L$rect$left, y = L$rect$top, legend = c('Group A', 'Group B'), col=rep(NA,2), lty=c(1,1), ncol=1, x.intersp = 3, bg = NA)

Answer 2

检查一下：

library(lattice)

myPCH <- 15:17
Data  <- rnorm(50)
Index <- seq(length(Data))

xyplot(Data ~ Index, 
       pch = myPCH, col=1:2,
       key = list(space = "right", adj=1,
                  text = list(c("a", "b", "c"), cex=1.5),
                  points = list(pch = myPCH),
                  points = list(pch = myPCH,col=2)))