question about determining the correct number of clusters (documentation)

I have a question about determining the correct number of clusters (in k-means clustering).

In the documentation, there is a section about 'determining the correct number of clusters'. Please help me understand what the arguments in the table are for: iter (which would mean iterations), phase (?), num (?), and sum(?).

In the example, you will see:

Best total sum of distances = 1771.1

Here are my questions:

1. Are we going for the best total sum of distances?
2. From here, how are we able to determine that 4 is indeed the correct?

Answer 1

[Bernhard Suhm]

You can use the silhouette plot or evalclusters function to evaluate the quality of your clustering. There's a little more info in this previous answer.