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Re: Re: Question - Cluster Analysis

  • To: mathgroup at smc.vnet.net
  • Subject: [mg89857] Re: [mg89842] Re: Question - Cluster Analysis
  • From: DrMajorBob <drmajorbob at att.net>
  • Date: Mon, 23 Jun 2008 02:45:55 -0400 (EDT)
  • References: <g3ihn2$fb6$1@smc.vnet.net>
  • Reply-to: drmajorbob at longhorns.com

That's a much nicer way to parse the Clusters. Thanks!

Bobby

On Sun, 22 Jun 2008 02:24:29 -0500, magma <maderri2 at gmail.com> wrote:

> On Jun 21, 11:30 am, Steve Mahoney <patrick.bernh... at gmx.net> wrote:
>> Hello,
>>
>> I have a question regarding hierarchical cluster analysis. One measure  
>> to determine the number of clusters is the so called elbow criteria,  
>> which is just a list of the single distances between the clusters.
>>
>> These values are inside the results from the Agglomerate function, but  
>> I am not able to extract them to a list.
>>
>> data = {{1, 2, 2}, {1, 3, 3}, {2, 4, 2}, {5, 4, 3}, {5, 4, 4}, {7, 6,  
>> 7}};
>>
>> Agglomerate[data]
>>
>> Cluster[Cluster[
>>   Cluster[Cluster[{1, 2, 2}, {1, 3, 3}, 2, 1, 1], {2, 4, 2}, 3, 2, 1],  
>> Cluster[{5, 4, 3}, {5, 4, 4}, 1, 1, 1], 10, 3, 2], {7, 6, 7}, 17, 5, 1]
>>
>> --> now I have to extract the values manually
>>
>> elbowcriterium = ListLinePlot[{17, 10, 3, 2, 1}]
>>
>> --> suggesting three clusters
>>
>> Thanks a lot for a suggestion, how to handle this, which would be  
>> really helpful for me!
>
> Hello,
> this was a good excuse for me to learn some cluster analysis in the
> past 2 hours !
> Ok, now I know what you are talking about, so this is your function
>
> ElbowCriterium[
>   cl_Cluster] := {cl[[3]], ElbowCriterium[cl[[1]]],
>    ElbowCriterium[cl[[2]]]} // Flatten
>
> ElbowCriterium[x_] := {}
>
> On your data:
>
> data = {{1, 2, 2}, {1, 3, 3}, {2, 4, 2}, {5, 4, 3}, {5, 4, 4}, {7, 6,
>     7}};
>
> Agglomerate[data] // ElbowCriterium
>
> the answer is....
>
> {17, 10, 3, 2, 1}
>
>
>



-- 
DrMajorBob at longhorns.com


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