Basic data types

The NDA has few basic data types by which all the data management is defined:

Data field (field, f):

The basic item is a data field which corresponds to a data vector. The values of the field must have the same type which can be integer, floating point or string.

Data frame (data, d):

The data frame corresponds to a data in matrix form. It can have data fields which are required to have the same length, but the fields can have different data types. One data record is defined as values collected from the fields in the data frame with the same index.

Classified data frame (cldata, c):

The classified data frame corresponds to a classification. The frame has fields which are integer-type, but they can have different lengths. One field in the frame corresponds to a class and integer values in the fields are references to items which are classified to a class by some classifier. For instance, classes may have the indexes of the data record in some data frame.

Structures:

There are such structural information which is difficult to represent by these three types. Thus, the system can store any structures, but operations must be defined separately for them. Some typical structures are the following:

TS-SOM:

The structure of the TS-SOM is one specific structure type implemented in the current version. However, note that a weight matrix is not included in this type, but weights are stored in a data frame.

Graphics:

Graphics is also handled as a structure.

Frames (data and classified data) include actually references to fields. One field can be referred from several frames, for instance, when the command select is used. This must be noted when frames and fields are deleted. When a frame is deleted, typically all of its fields are also deleted if they are not referred from other frames. As well, there are operations to unlink fields from frames and to delete a field when all the references from frames are also removed.

The order of the fields has not been defined explicitly. However, some operations suppose that fields are ordered. The operation select creates fields in a given order to a frame. Correspondingly the listing operation shows fields in their order.