[R] mva - kmeans (repetitive requests)

[Athula Herath]

Hi All,

Should I get two different results if I were to repeat the kmeans
clustering on the same data set?


R : Copyright 2000, The R Development Core Team
Version 1.1.1  (August 15, 2000)


The following code

library(mva)
data(iris)
kmeans(iris[1:4],5,20)

generates:

$cluster
  [1] 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5
5 5 5 5
 [38] 5 5 5 5 5 5 5 5 5 5 5 5 5 2 2 2 3 2 3 2 4 2 3 4 3 3 2 3 2 3 3 2 3
2 3 2 2
 [75] 2 2 2 2 2 3 3 3 3 2 3 2 2 2 3 3 3 2 3 4 3 3 3 2 4 3 1 2 1 1 1 1 3
1 1 1 2
[112] 2 1 2 2 1 1 1 1 2 1 2 1 2 1 1 2 2 1 1 1 1 1 2 2 1 1 1 2 1 1 1 2 1
1 1 2 2
[149] 1 2

$centers
  Sepal.Length Sepal.Width Petal.Length Petal.Width
1     6.912500    3.100000     5.846875     2.13125
2     6.252500    2.855000     4.815000     1.62500
3     5.620833    2.691667     4.075000     1.26250
4     5.000000    2.300000     3.275000     1.02500
5     5.006000    3.428000     1.462000     0.24600

$withinss
[1] 18.703437 13.624750  5.219167  0.295000 15.151000

$size
[1] 32 40 24  4 50

And if I do a further  kmeans(iris[1:4],5,20) gives me:

$cluster
  [1] 5 1 1 1 5 5 1 5 1 1 5 1 1 1 5 5 5 5 5 5 5 5 1 5 1 1 5 5 5 1 1 5 5
5 1 1 5
 [38] 5 1 5 5 1 1 5 5 1 5 1 5 1 2 2 2 3 2 3 2 3 2 3 3 3 3 2 3 2 3 3 2 3
2 3 2 2
 [75] 2 2 2 2 2 3 3 3 3 2 3 2 2 2 3 3 3 2 3 3 3 3 3 2 3 3 4 2 4 2 4 4 3
4 4 4 2
[112] 2 4 2 2 4 4 4 4 2 4 2 4 2 4 4 2 2 4 4 4 4 4 2 2 4 4 2 2 4 4 4 2 4
4 4 2 2
[149] 4 2

$centers
  Sepal.Length Sepal.Width Petal.Length Petal.Width
1     4.704545    3.122727     1.413636   0.2000000
2     6.257143    2.861905     4.850000   1.6333333
3     5.532143    2.635714     3.960714   1.2285714
4     6.950000    3.106667     5.866667   2.1533333
5     5.242857    3.667857     1.500000   0.2821429

$withinss
[1]  3.114091 14.800238  9.749286 17.555000  4.630714

$size
[1] 22 42 28 30 28

In S-Plus (2000)  the repetitive executions gives us the same result.
Are these  results  generated by R consistent?

Thanks,

Athula.






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