Occurrences and Co-occurrences

The Occurrences, in fact, are quantities which result from the computation of how many times (frequences) a single lexical unit (LU)occurs within a corpus or within the context units (CU) in which it is subdivided.

Their distribution can be represented in contingency tables as follows:

Co-occurrences, then, are quantities which result from a computation of how many times two or more lexical units are present together in the same elementary contexts (EC).

Their distribution can be represented in tables such as the following:

With a simple transformation, the "A" type table (rectangular) can be transformed into "B" type (squared and symmetrical) in which for each pair of lexical units the quantity of their co-occurrences is indicated, that is the total number of the elementary contexts in which they are present together.

In T-LAB text analysis is mostly carried out by the study of relationships among occurrences and co-occurrences, either through specific association indexes, or through the use of multidimensional statistical techniques like cluster analysis and correspondence analysis