Re: [Fwd: Re: [Databionic-ESOM-User] ESOM]

[<fa...@in...>]

>> did you save the class mask explicitely? this should be done
>> automatically but might be a point of error.
> 
> How can the class mask (.cls file ) be created automatically?
> I though that when we want to create a class mask (.cls) we
> 
> enable the classmask tab and select regions on the map with the
> polygon. a right mouse click will finish the selection and one class will
> be created and shown in the tab.
> 
> When I have created all the classes I select to save the cls file
> manually from the "class mask" tab.
> Right or wrong? So how is a class mask file created automatically?

right. you always have to _create_ the class mask manually. the question
was, however, whether this mask gets saved to disk in a *.cls file
automatically. it does not seem to be, i just checked it. even saving it
manually did't save all problems. try this workaround:

- create the class mask
- save the class mask
- load the class mask

now the following tools should definitely know about the existence of
the class mask and use it.

this does not explain the bm=-1 messages you reported earlier, however,
i did not get these in my test. but maybe you can get one step further
and tell us about it.

> 2.When I want to create the cls file for the test set sometimes when I
> select classify the .cls file is not created automatically.
> I think that sometimes the cls file is created in the "classes" tab and
> can be saved from there.
> Right or wrong?

both. the classification result should be listed in the classes tab and
got saved in a file on disk (*_projected.cls). you can always manually
save it under a different name or folder if you wish.

> 3.Sometimes when I load an .lrn file and select to perform
> z-transformation the file that is created includes non readable
> characters and I cannot explain why is this happening.

this sounds weird. which characters? maybe a "?"? that would mean a NaN
and could be caused by a column with constant value (-> std = 0 ->
division by zero).

> 4.The whole procedure of training with a train set creating a class
> mask, projecting a test set and creating a new cls file for the train
> set belong is the category of unsupervised classification?

no. unsupervised classification is a term sometimes used for clustering.
i think the term is misleading, because (supervised) classification and
(unsupervised) clustering are completely different problems. the
procedure you describe is classification because you have a labeled
training set that you assume to be the ground truth and use it to define
the class mask. this is similar to training a decision tree. in fact
projecting data on an esom with a classmask is somewhat a sophisticated
version of k-nearest neighbor classification with k = 1. a new data
point is assigned the same label as it's nearest prototype in the data
space as defined by the trained esom. but you have the additional
benefit of visually defining the classes and allowing regions with no
class label.

if you create the class mask without any given labels, you have an
unsupervised process. then i would call it clustering with a sample and
applying the results to a larger data set with esom classification.

bye
fabian