All1

All1 is not a single, universally recognized term; rather, it appears across disciplines as a label or shorthand for "all ones" in various forms. Commonly, it is used informally to denote a construct consisting of ones, such as the all-ones vector or the all-ones matrix.

In mathematics, the all-ones vector of length n is the column (or row) vector with every entry equal to 1, often written as 1_n. The all-ones matrix, sometimes denoted J, has every entry equal to 1; for an n-by-m matrix, J has rank 1 and is used in analyses involving centering, projections, or as a simple kernel.

In computing and programming, all1 may appear as a variable name, a function, or a constant representing a vector or mask of ones. The exact meaning is defined by the surrounding code or mathematical context, and the term is not standardized across languages or libraries.

Other uses include project names, dataset identifiers, or file labels. When encountering all1, it is best to consult local definitions or documentation to determine whether it represents a mathematical object, a software constant, or an arbitrary label.

Related concepts include the all-ones vector and the all-ones matrix, commonly denoted 1_n and J, respectively.