N1×p

n1×p is a notation that can denote either the product of two quantities n1 and p or the dimensions of a two‑dimensional array with n1 rows and p columns. The exact meaning depends on context.

In data analysis and linear algebra, n1×p commonly describes the size of a matrix. A matrix with n1 rows and p columns is said to have dimensions n1 by p (often written as n1×p). For example, a data matrix X with 100 observations and 20 features has the size 100×20. The transpose of this matrix would have size 20×100.

As a product, n1×p represents the multiplication of two numbers, yielding a scalar if both terms are scalars. For instance, if n1 = 4 and p = 3, then n1×p = 12. In some contexts the letters n and p stand for specific quantities such as sample size and number of features; in others, they are merely symbolic placeholders.

Ambiguity can arise when the same symbols appear in different parts of a formula. Without sufficient context, n1×p could be read as a dimension specification or as a product. Parentheses or additional notation (such as X ∈ R^{n1×p} to indicate a real-valued matrix of that size) help clarify meaning.

Related concepts include matrix dimensions, the role of data matrices in statistics and machine learning, and operations on matrices such as multiplication and transposition. Maintaining consistent interpretation of n1 and p within a given framework reduces confusion.