SOM Toolbox | Online documentation | http://www.cis.hut.fi/projects/somtoolbox/ |

Default values for map topology and training parameters.

sT = som_topol_struct('argID',value,...); sT = som_topol_struct(value,...);

This function is used to give sensible values for map topology (ie. map size). The topology struct is returned. The topology struct has three fields: '.msize', '.lattice' and '.shape'. Of these, default value for '.lattice' is 'hexa' and for '.shape' 'sheet'. Only the '.msize' field depends on the optional arguments: 'dlen', 'munits' and 'data'. The value for '.msize' field is determined as follows. First, the number of map units is determined (unless it is given). A heuristic formula of 'munits = 5*sqrt(dlen)' is used to calculate it. After this, the map size is determined. Basically, the two biggest eigenvalues of the training data are calculated and the ratio between sidelengths of the map grid is set to the square root of this ratio. The actual sidelengths are then set so that their product is as close to the desired number of map units as possible. If the lattice of the grid is 'hexa', the ratio is modified a bit to take it into account. If the lattice is 'hexa' and shape is 'toroid', the map size along the first axis must be even.

argID (string) Argument identifier string (see below). value (varies) Value for the argument (see below). The optional arguments can be given as 'argID',value -pairs. If an argument is given value multiple times, the last one is used. The valid IDs and corresponding values are listed below. The values which are unambiguous (marked with '*') can be given without the preceeding argID. 'dlen' (scalar) length of the training data 'data' (matrix) the training data *(struct) the training data 'munits' (scalar) number of map units 'msize' (vector) map size 'lattice' *(string) map lattice: 'hexa' or 'rect' 'shape' *(string) map shape: 'sheet', 'cyl' or 'toroid' 'topol' *(struct) incomplete topology struct: its empty fields will be given values 'som_topol','sTopol' = 'topol'

sT (struct) The topology struct.

The most important optional argument for the default topology is 'data'. To get a default topology (given data) use: sTopol = som_topol_struct('data',D); This sets lattice to its default value 'hexa'. If you want to have a 'rect' lattice instead: sTopol = som_topol_struct('data',D,'lattice','rect'); or sTopol = som_topol_struct('data',D,'rect'); If you want to have (close to) a specific number of map units, e.g. 100: sTopol = som_topol_struct('data',D,'munits',100);

som_make
| Initialize and train a map using default parameters. |

som_train_struct
| Default training parameters. |

som_randinint
| Random initialization algorithm. |

som_lininit
| Linear initialization algorithm. |

som_seqtrain
| Sequential training algorithm. |

som_batchtrain
| Batch training algorithm. |