Changes from version 1 to version 2
Version 2 of SOM Toolbox is considerably different from version 1. The major changes are in structs, preprocessing and visualization. Then there are a number of minor changes in the way the functions work, in the names of the functions, and in values of default parameters. In addition, there are a lot of new auxiliary functions.
Changes in structs
The most essential changes are in the structs. Therefore, two functions have been provided som_vs2to1 and som_vs1to2 which can be used to convert between version 1 and 2 structs.
Map structThe changes in the map struct are:
Data structThe changes in the data struct are:
Topology structThis is a new struct, which contains the fields .msize, .lattice and .shape previously part of map struct. There's also a change in the values that the .shape field can get. The value 'rect' referring to the shape of the map has been changed to 'sheet'.
Training structThere are a number of changes in the contents of this struct. Field .data_name from map struct has been brought here, and fields .neigh and .mask have been copied here (also from map struct).
Normalization structThe normalization struct now has normalization information for only one variable (as opposed to version 1, when it had information on all variables). For further information see notes on preprocessing below.
The functions involved with preprocessing have completely changed. Instead of som_normalize_data and som_denormalize_data, the functions are som_normalize, som_denormalize and som_norm_variable. The functions som_normalize and som_denormalize envelope the operations of adding and removing normalization operations to data and map structs, and call som_norm_variable to do the actual work.
Function som_norm_variable performs normalization operations for a single variable at a time. The possible actions are 'init', 'do' and 'undo', and the possible normalization operations are 'var', 'range', 'log', 'histD' and 'histC'. Of these 'var' equals 'som_var_norm', 'range' equals 'som_lin_norm' and 'histD' equals 'som_hist_norm' of version 1. Normalization of vectors to unit length ('som_unit_norm') is not implemented in version 2. New normalization operations in version 2 are 'log' and 'histC'.
In version 1, the relative performance of sequential, batch and SOM_PAK algorithms were: 23:1.3:1. Now the relative performance is 3:1.2:1. The speed of batch training has not improved that much, but its memory consumption is only fractions of what it was before.
Monday, 09-Oct-2000 12:53:06 EEST