Question

我正在ggplot2中绘制100个不同的椭圆图。我希望绘图上的椭圆/多边形稍微半透明，以使上面带有最多线条的区域变暗，而带有一个椭圆的区域将变得很暗。

The opacity I want与the opacity im currently getting

但是，无论我将alpha更改为什么，它似乎都没有效果？我在做什么错了？

ggplot(data = cssibernobk, aes(iso1, iso2)) +
  scale_fill_manual(name = "Marlin Species", labels = c("Blue Marlin", "Striped Marlin"),values=c(col_list)) +
  geom_polygon(data = ellipse_dfcs,
               show.legend = FALSE,
               mapping = aes(iso1, iso2,
                             group = ellipse_dfcs$group,
                             color = factor(group),
                             fill = factor(group)), fill = NA, alpha = 0.2) + 
  scale_color_manual(values = col_list)+
  geom_point(colour="black", shape=21, size = 2, 
             aes(fill = factor(group))) + 
  ylab(expression(paste(delta^{34}, "S (\u2030)")))+ 
  xlab(expression(paste(delta^{13}, "C (\u2030)")))+ 
  theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank(),
        panel.background = element_blank(), axis.line = element_line(colour = "black"))

我添加了一些数据：

dput(cssibernobk[1:10,])
structure(list(iso1 = c(-19.0666624548854, -17.8943955612859, 
-18.9928609367509, -16.4710761874456, -18.2727144857982, -20.5069897964015, 
-20.5966996037602, -17.5454265065267, -16.4393689881177, -17.4617536511442
), iso2 = c(19.4934410976126, 19.2364832949763, 19.7701196888491, 
19.837594669008, 19.7147010622141, 20.3802264543413, 20.4655925249838, 
19.0895171633117, 19.7264242586365, 19.2537859386917), group = c(1, 
1, 1, 1, 1, 1, 1, 1, 1, 1), community = c(1, 1, 1, 1, 1, 1, 1, 
1, 1, 1)), row.names = c(NA, -10L), class = c("tbl_df", "tbl", 
"data.frame"))

dput(ellipse_dfcs[1:10,])
structure(list(id = c("1", "1", "1", "1", "1", "1", "1", "1", 
"1", "1"), iso1 = c(-15.3019878272902, -15.4740783680741, -15.6530442971316, 
-15.8381649818314, -16.0286950065133, -16.2238671740144, -16.4228955949008, 
-16.6249788519676, -16.8293032272625, -17.0350459786413), iso2 = c(20.3654052739855, 
20.44444500941, 20.5195305006846, 20.5903594050369, 20.6566465194678, 
20.718124929163, 20.7745470822651, 20.8256857866775, 20.8713351248865, 
20.9113112831188), community = c("1", "1", "1", "1", "1", "1", 
"1", "1", "1", "1"), group = c("1", "1", "1", "1", "1", "1", 
"1", "1", "1", "1")), row.names = c(NA, 10L), class = "data.frame")

为帮助喝彩！

Answer 1

问题是您指定的是alpha=，但是它应用于行的fill=，而不是行的color=。例如，在geom_line()中，可以使用alpha=使行透明，但是geom_polygon()则不是这样。由于很难使用您的布景来显示，因此让我用一个示例布景来演示：

# I dunno, I'm making shapes...
d <- data.frame(id=c(rep('this',4),rep('that',4)), x=c(0,1,1,0.5,0.5,2,0.5,0.5), y=c(0,0,2,3,0.5,2,2,1))

p <- ggplot(d, aes(x,y)) + theme_bw()
p + geom_polygon(aes(color=id), size=1.5)

确实，从未有过如此美丽的图画。如果我们对此应用alpha=，您会看到只有填充会受到影响：

p + geom_polygon(aes(color=id), size=1.5, alpha=0.2)

那么我们如何解决呢？好吧，您需要以另一种方式指定alpha，即使用alpha(): the function。您可能会认为可以在aes()中使用并直接应用于color=美学……但是您会错的。 aes(color=alpha(id, 0.2))无法正常工作，因为alpha()希望发送给您实际的颜色名称，而不是像ggplot2这样的要素名称。不过，您可以在alpha()中指定scale_color_manual()，这就是我们得出答案的地方：

p + geom_polygon(aes(color=id), size=1.5, alpha=0.2) +
  scale_color_manual(values=alpha(c("this"='blue', "that"='red'),0.2))

从中可能很难看到，但是线条的颜色是透明的。您可以在没有alpha设置的情况下与相同颜色进行比较：

p + geom_polygon(aes(color=id), size=1.5, alpha=0.2) +
  scale_color_manual(values=c("this"='blue', "that"='red'))

现在很明显，您需要更改scale_color_manual()行。我认为这应该可行：

  scale_color_manual(values = alpha(col_list, 0.2))

如何更改ggplot中椭圆的半透明性？

1 个答案: