将ggplot中的点的alpha设置为数字向量

I am trying to create an NMDS plot using ggplot. In addition to the standard plotting of points (communities/assemblages) and hulls etc. I would also like to adjust the alpha of each point.

我正在尝试使用ggplot创建NMDS图。除了点（社区/组合）和船体等的标准绘图之外，我还想调整每个点的alpha。

I have calculated a vector of numeric values from 0-1 (called "Alpha") which reflects the timing of the surveys which correspond to each point and I would like to use this to modify the alpha of each point. Thus far I have been using variations on the theme of:

我已经计算了一个0-1的数值向量（称为“Alpha”），它反映了与每个点相对应的调查的时间，我想用它来修改每个点的alpha。到目前为止，我一直在使用以下主题的变体：

 ggplot() +
     geom_point(data = data.scores, aes(x = NMDS1, y = NMDS2, colour =Treatment), size = 3) +
     scale_colour_manual(values = c("Burnt" = "black", "Grazed" = "tan4","Control" = "green4")) +
     scale_alpha_manual(values = Alpha) +
     geom_polygon(data = hull.data, aes( x = NMDS1, y = NMDS2, colour = Treatment),
                  linetype = "dashed", fill = NA) +
     coord_equal() +
     theme_bw() +
     theme(panel.border = element_blank(), panel.grid.major = element_blank(),
           panel.grid.minor = element_blank(), axis.line = element_line(colour = "black"),
           legend.position="top")

This has only got me plots where the alpha of all the points is 1, the alpha is not 1 but is set to the same value (presumably the first value in my vector) or error messages. Does anyone have any idea what I'm doing wrong?

这只得到了我所有点的alpha为1，alpha不是1但是设置为相同值（可能是我向量中的第一个值）或错误消息的图。有谁知道我做错了什么？

For reference I was able to create what I want using base R graphics fairly easily but I need my plot to be a ggplot graphic:

作为参考，我能够相当容易地使用基本R图形创建我想要的东西，但我需要我的情节是ggplot图形：

1 个解决方案

#1

ggplot() syntax expects the values being mapped for a layer to be passed in that layer, so in geom_point(), and not by adding a scale. So right now you are not defining which layers you want the alpha scale to be applied to, thus all are being shown as alpha = 1 (the default).

ggplot（）语法期望为图层映射的值在该图层中传递，因此在geom_point（）中，而不是通过添加比例。所以现在你没有定义你想要应用alpha刻度的图层，因此所有图层都显示为alpha = 1（默认值）。

You can just use the raw vector directly in geom_point(). Using a reproducible example with mtcars:

您可以直接在geom_point（）中使用原始向量。使用mtcars的可重现示例：

library(ggplot2)
set.seed(1)

# sim your Alpha
Alpha <- runif(nrow(mtcars))

ggplot(data = mtcars, aes(mpg, hp)) +
    geom_point(alpha = Alpha)

scale_alpha_manual() won't have any effect on this plot since you are not mapping anything with aes(alpha = ...).

scale_alpha_manual（）不会对此绘图产生任何影响，因为您没有使用aes（alpha = ...）映射任何内容。

#1