GGbiplot为某些数据点添加了一些额外的颜色

Question

是否可以在R中的ggbiplot包中标记某些特殊数据点，例如数据点，其中Alcohol = 13.2为另一种颜色，然后在群集中。我想强调一些具体的数据点。

data(wine)
wine.pca <- prcomp(wine, scale. = TRUE)
print(ggbiplot(wine.pca, obs.scale = 1, var.scale = 1, groups = wine.class, 
   ellipse = TRUE, circle = TRUE))

Answer 1

我不确定是否可以在ggbiplot调用中完成此操作，但通过添加其他图层肯定是可行的。这是一个例子：

library(ggbiplot)

data(wine)
wine.pca <- prcomp(wine, scale. = TRUE)
p <- ggbiplot(wine.pca, obs.scale = 1, var.scale = 1, groups = wine.class, 
               ellipse = TRUE, circle = TRUE)

现在对要突出显示的点进行分组：

wine.pca$x[wine$Alcohol == 13.2, 1:2, drop = FALSE] #drop = FALSE to keep matrix class

并将其作为data提供给geom_point：

p + geom_point(data = wine.pca$x[wine$Alcohol == 13.2, 1:2, drop = FALSE],
              aes(x = PC1, y = PC2), color = "black")

您也可以这样做：

p + geom_point(data = wine.pca$x[wine$Alcohol == 13.2, 1:2, drop = FALSE],
               aes(x = PC1, y = PC2), color = "black", shape = 21, size = 7)

但是如果你想突出很多点，这可能会太多了：

p + geom_point(data = wine.pca$x[wine$Alcohol >= 13.2, 1:2],
               aes(x = PC1, y = PC2), color = "black", shape = 21, size = 7)

Answer 2

是的，因为ggbiplot是有效的ggplot2对象，您可以像在其他ggplots上一样添加geom。

cond <- wine.pca$x[which(wine$Alcohol == 13.2),]
cond[1:2]

返回：

       PC1        PC2 
-2.2032498 -0.3324551 

这是代码。请注意，我们使用geom_point并分别指向PC1和PC2的x轴和y轴wine$Alcohol==13.2：

library(ggbiplot)
data(wine) 
wine.pca <- prcomp(wine, scale. = TRUE)
ggbiplot(wine.pca, obs.scale = 1, var.scale = 1, groups = wine.class, ellipse = TRUE, circle = TRUE) + 
geom_point(aes(x=cond[1], y=cond[2]), col="goldenrod2", size=3)