大家好!我被要求在 R 上创建一个 K 均值算法，但我并不真正了解这门语言，所以我在互联网上找到了一些示例代码，并决定使用。我研究了它，了解了其中使用的功能，并对其进行了一些修正，因为它运行得不太好。代码如下:
# Creating a sample of data
y=rnorm(500,1.65)
x=rnorm(500,1.15)
x=cbind(x,y)
centers <- x[sample(nrow(x),5),]
# A function for calculating the distance between centers and the rest of the dots
euclid <- function(points1, points2) {
distanceMatrix <- matrix(NA, nrow=dim(points1)[1], ncol=dim(points2)[1])
for(i in 1:nrow(points2)) {
distanceMatrix[,i] <- sqrt(rowSums(t(t(points1)-points2[i,])^2))
}
distanceMatrix
}
# A method function
K_means <- function(x, centers, euclid, nItter) {
clusterHistory <- vector(nItter, mode="list")
centerHistory <- vector(nItter, mode="list")
for(i in 1:nItter) {
distsToCenters <- euclid(x, centers)
clusters <- apply(distsToCenters, 1, which.min)
centers <- apply(x, 2, tapply, clusters, mean)
# Saving history
clusterHistory[[i]] <- clusters
centerHistory[[i]] <- centers
}
structure(list(clusters = clusterHistory, centers = centerHistory))
}
res <- K_means(x, centers, euclid, 5)
#To use the same plot operations I had to use unlist, since the resulting object in my function is a list of lists,
#and default object is just a list. And also i store the history of each iteration in that object.
res <- unlist(res, recursive = FALSE)
plot(x, col = res$clusters5)
points(res$centers5, col = 1:5, pch = 8, cex = 2)
它在这个简单的矩阵上运行良好。但有人要求我在 iris 上使用它:
head(iris)
a <-data.frame(iris$Sepal.Length, iris$Sepal.Width, iris$Petal.Length, iris$Petal.Width)
centers <- a[sample(nrow(a),3),]
iris_clusters <- K_means(a, centers, euclid, 3)
iris_clusters <- unlist(iris_clusters, recursive = FALSE)
head(iris_clusters)
问题是它不起作用。错误是:
Error in distanceMatrix[, i] <- sqrt(rowSums(t(t(points1) - points2[i, :
number of items to replace is not a multiple of replacement length
我知道物体的尺寸不匹配，但我不明白为什么。这就是我寻求帮助的原因。我提前对这段代码中可能存在的所有愚蠢之处表示歉意，但我还不太熟悉这门语言，所以不要对我评价太严厉。谢谢!
最佳答案
您的实现应该适用于简单的类型转换
iris_clusters <- K_means(as.matrix(a), as.matrix(centers), euclid, 3) # 3 iterations
iris_clusters <- unlist(iris_clusters, recursive = FALSE)
# plotting the clusters obtained on the first two dimensions at the end of 3rd iteration
plot(a[,1:2], col = iris_clusters$clusters3, pch=19)
points(iris_clusters$centers3, col = 1:5, pch = 8, cex = 2)
head(iris_clusters)
# cluster assignments and centroids computed at different iterations
$clusters1
[1] 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 2 2 3 2 3 2 3 2 3 3 3 3 2 3 3 3 3 3 3 2 3 2 2 3 3
[77] 2 2 3 3 3 3 3 2 3 3 2 3 3 3 3 2 3 3 3 3 3 3 3 3 1 2 1 2 1 1 3 1 1 1 2 2 2 2 2 2 2 1 1 2 1 2 1 2 1 1 2 2 2 1 1 1 2 2 2 1 2 2 2 2 1 2 2 1 1 2 2 2 2 2
$clusters2
[1] 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 2 2 2 2 2 2 3 2 3 3 2 2 2 3 2 2 2 2 3 2 2 2 2 2 2
[77] 2 2 2 3 3 3 2 2 2 2 2 2 2 2 2 2 2 3 2 2 2 2 3 2 1 2 1 2 1 1 2 1 1 1 2 2 1 2 2 2 2 1 1 2 1 2 1 2 1 1 2 2 2 1 1 1 2 2 2 1 2 2 2 1 1 2 2 1 1 2 2 2 2 2
$clusters3
[1] 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 2 2 2 2 2 2 3 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
[77] 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 2 2 2 2 3 2 1 2 1 2 1 1 2 1 1 1 2 2 1 2 2 2 2 1 1 2 1 2 1 2 1 1 2 2 1 1 1 1 1 2 2 1 1 2 2 1 1 1 2 1 1 1 2 2 2 2
$centers1
iris.Sepal.Length iris.Sepal.Width iris.Petal.Length iris.Petal.Width
1 7.150000 3.120000 6.090000 2.1350000
2 6.315909 2.915909 5.059091 1.8000000
3 5.297674 3.115116 2.550000 0.6744186
$centers2
iris.Sepal.Length iris.Sepal.Width iris.Petal.Length iris.Petal.Width
1 7.122727 3.113636 6.031818 2.1318182
2 6.123529 2.852941 4.741176 1.6132353
3 5.056667 3.268333 1.810000 0.3883333
$centers3
iris.Sepal.Length iris.Sepal.Width iris.Petal.Length iris.Petal.Width
1 7.014815 3.096296 5.918519 2.155556
2 6.025714 2.805714 4.588571 1.518571
3 5.005660 3.369811 1.560377 0.290566
关于r - K-均值算法，R，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40979777/