R：如何将噪声簇添加到 DBSCAN 图中

Question

我正在尝试绘制 DBSCAN 结果。这是我到目前为止所做的。我的距离矩阵是 here.

dbs55_CR_EUCL = dbscan(writeCRToMatrix,eps=0.006, MinPts = 4, method = "dist")

plot(writeCRToMatrix[dbs55_CR_EUCL$cluster>0,], 
     col=dbs55_CR_EUCL$cluster[dbs55_CR_EUCL$cluster>0],
     main="DBSCAN Clustering K = 4 \n (EPS=0.006, MinPts=4) without noise",
     pch = 20)

剧情如下：

当我尝试绘制包括噪声簇在内的所有簇时，我只能在图中看到 2 个点。

我要找的是

将噪声簇中的点添加到图中，但使用不同的符号。类似下图的东西

像下图那样给集群区域加阴影

Answer 1

噪声簇的 id 为 0。R 图通常忽略颜色 0，因此如果要显示噪声点（黑色），则需要执行以下操作：

plot(writeCRToMatrix, 
  col=dbs55_CR_EUCL$cluster+1L,
  main="DBSCAN Clustering K = 4 \n (EPS=0.006, MinPts=4) with noise",
  pch = 20)

如果你想要一个不同的噪声符号，那么你可以执行以下操作（改编自手册页）：

library(dbscan)
n <- 100
x <- cbind(
     x = runif(10, 0, 10) + rnorm(n, sd = 0.2),
     y = runif(10, 0, 10) + rnorm(n, sd = 0.2)
)

res <- dbscan::dbscan(x, eps = .2, minPts = 4)
plot(x, col=res$cluster, pch = 20)
points(x[res$cluster == 0L], col = "grey", pch = "+")

这是将为每个集群创建阴影凸包的代码

library(ggplot2)
library(data.table)
library(dbscan)


dt <- data.table(x, level=as.factor(res$cluster), key = "level")
hulls <- dt[, .SD[chull(x, y)], by = level]

### get rid of hull for noise
hulls <- hulls[level != "0",]

cols <- c("0" = "grey", "1" = "red", "2" = "blue")

ggplot(dt, aes(x=x, y=y, color=level)) +
  geom_point() +
  geom_polygon(data = hulls, aes(fill = level, group = level),
    alpha = 0.2, color = NA) +
  scale_color_manual(values = cols) +
  scale_fill_manual(values = cols)

希望对您有所帮助。

R：如何将噪声簇添加到 DBSCAN 图中

R: How to add the noise cluster into DBSCAN plot

r

plot

cluster-analysis

dbscan