In what type of data does each row represent one time point per subject?

In long data format, each row corresponds to one time point for each subject, allowing for a clear representation of how variables change over time across different subjects. This structure makes it easy to analyze time series data, as it aligns well with statistical modeling techniques and visualization methods typically used in time series analysis. Each subject's observations are stacked vertically, which facilitates functions like grouping, summarizing, or plotting.

When considering other types of data, while spatial data deals with geographical locations and may represent data in multiple formats, it does not convey time points per subject in the same way as long data does. Wide data, on the other hand, organizes data in a horizontal format where each subject could have multiple measurements across the columns, making it less efficient for time-based analysis. Temporal data, while relevant to time-based studies, does not specifically imply the organization of data as long format does and may encompass various structures beyond the standardized long format.