"x-means k max"

I'am trying to apply x-means algorithm for clusterizar some data, the issue is that when I select the operator "x-means" has the parameters k and k min = 2 max = 60
The problem is that it does not let me select a k max below 60. this is a restrigcion algorithm or a bug?
regards
Best Answer
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Hi,
RapidMiner Studio 7.5 will reduce the selectable minimum to 3.
Regards,
Marco
2
Answers
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At a first glance this looks like a bug. I will create an internal ticket requesting to investigate this issue.
Best regards,
Marius0 -
It seems you still the same issue, I'm also not able to select anything but 60
It works if you add it as a parameter directly in the xml (eg <parameter key="k_max" value="20"/>), looks like this is not added by default
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@kayman I do not think this is necessarily a bug---based on parameter description, it simply is the minimum value that is accepted as the maximum range for x-means.
k max (optional) The maximal number of clusters which should be detected. Type: integer
Range: 60 - +∞
Default: 60It looks like the algorthim is still testing every value between 2 (default minimum) and 60 so I am not sure if it matters if you would prefer a smaller maximum, since it would be within your range.
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I see, didn't notice that to be honnest...
60 seems however like a fairly big number, the problem is that in my specific case the best value is typically below 20, and therefore it takes like 3 times the necessary amount of time to get the best prediction. In itself not such a big deal but when working with larger datasets it does make a nice difference.
Any reason why 60 is chosen, is there a statistical story behind that number (pure out of interest) ?
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Hi,
i've read the source code and there is no comment on why 60 is the min.. The class cites the paper: https://www.cs.cmu.edu/~dpelleg/download/xmeans.pdf for the implementation. Not sure if there is some argument in this one.
I will open up a ticket internally. If you desperatly need it you can extend the class and change the setting.
Best,
Martin
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Hi,
RapidMiner Studio 7.5 will reduce the selectable minimum to 3.
Regards,
Marco
2