Ytimekset

Ytimekset is a term used in some discussions of temporal data structures and spacetime modelling to denote collections of time points that share a fixed secondary coordinate, commonly denoted y. In this interpretation, a two-dimensional time-space plane uses t for time and y as a second axis representing, for example, spatial location, scenario index, or another dimension of interest. A ytimekset consists of all events with the same y value across times, i.e., { (t, y0) | t in T }. A family of ytimekset can be obtained by varying y across the domain, forming a partition of the data into cross-sections.

Properties: Each ytimekset is a subset of the time-space domain; they can be finite or infinite in extent. Under a standard indexing, each event belongs to exactly one ytimekset, while different ytimekset may be analyzed in parallel to study temporal dynamics conditioned on y. In purely temporal analyses, y can represent a fixed parameter such as a sensor or location.

Applications: Ytimekset concepts appear in data visualization, cross-sectional time-series analysis, and spacetime modelling for climate, traffic, or sensor networks. They support conditioning on secondary coordinates to compare temporal patterns across categories.

Relation to related concepts: Similar to grouping by a secondary dimension in panel data or cross-sectional time-series analysis; akin to slices or cross-sections in spacetime diagrams.

Limitations: The usefulness of ytimekset depends on the existence and meaningfulness of the secondary coordinate y; without this, the concept reduces to ordinary time series.