Re: [Databionic-ESOM-User] what if...

[<fa...@my...>]

Hi,

if you have two valleys separated by a mountain this corresponds to two
clusters on a coarse scale.

Please try to retrain without the points in the mountainous regions as
Christian suggested.

If you want more details than you can find with the sliders you can also
select all points in one valley, save the selection to a new (*.lrn)
file and train a new map only on this data. This will give you the most
detailed view into this region of the data space. Of course you can do
this for each valley.

Please note that normalizing the data and picking a good distance
function is crucial. If you want comparable results to PCA you need to
apply the same normalization, if any. Also note that EM creates clusters
that correspond to possibly overlapping Gaussian distributions in the
high dimensional space. ESOM tries to find clearly separable
non-overlapping clusters.

best
fabian

Christian Stamm wrote:
> Hi davide,
>
> Those results might tell you that there are no separable groups in your
> data. There is a few things you might try to clarify the situation.
>
> First of all use the Clip slider in the view tab to make finer structures
> visible in the existing map. It clips big heights in the U-Matrix, so the
> color gradient will be mapped over lower heights. Structures in those
> might be dominated by the big mountain right now and then become visible.
>
> You should also try and train another map without the suspected outliers,
> just to see what happens. You should also evaluate wether or not they are
> outliers using other methods like scatter plots.
>
> regards,
> Christian
>
>
>
>   
>> Hi againI'm trying to get something out of my ~4000 datapoints in 123
>> attributes. Some clustering techniques (i.e. EM clustering) and other data
>> analysis tools (i.e. PCA) tell me I can divide my dataset in 3 or 4 big
>> "groups".
>> I'm trying now ESOM tools and it looks like I have a mountain and two
>> orthogonal valleys (on a toroid map). On the mountain I have one group
>> (are
>> those all outliers?) in the valleys I have all remaining data. It happens
>> that data that were in the same group in other analysis are still next to
>> each other but, since they are in the same valley (actually a plain under
>> mountains...), I should say that they cannot be clustered with ESOM
>> tools...
>> Do you have any hint to get out this?
>>
>> Thanks
>>
>> d
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