R pch中的传奇没有填满

Question

尝试使用pch绘制一个图例，我的理解是这些应该被填充，但似乎不是这样。这是windows图形的问题吗？

legend(36, 79,
    legend = c(expression("a"["a"]), expression("b"["b"]), expression("c"["c"])),
    pch = c(21, 8, 24), col = c(grey(0.1), grey(0.3), grey(0.5)),
    cex = 1.3, bty = "n"
)

通常不会发布，但这是为了提交论文，图中的图例和图形应该匹配 谢谢！

Answer 1

我们需要pt.bg参数填写：

见下面的例子：

#dummy data
set.seed(123)
df <- data.frame(x=runif(10),y=runif(10),
                 colour=rep(c("blue","green"),5),
                 background=rep(c("grey30", "grey70"),5),
                 shape=rep(c(21,24),5),stringsAsFactors = FALSE)

#plot
plot(df$x,df$y,col=df$colour,bg=df$background,pch=df$shape,cex=2)
points(x=0.5,y=0.5,pch=8,col="red",cex=2)

#add legend, pt.bg is need to fill in the background of the shape
legend(0.01,0.5,
       legend = c(expression("LBM"["MR-AC"]),
                  expression("LBM"["Formula"]),
                  expression("LBM"["MR-AC corrected"])),
       pch = c(21,24,8),
       col = c("blue","green","red"),
       pt.bg = c("grey30","grey70"),
       cex=2)