Understanding the Language

Defining a Matrix

The fundamental data object on which all Interactive Matrix Language commands operate is a two-dimensional (row × column) numeric or character matrix. By their very nature, matrices are useful for representing data and efficient for working with data. Matrices have the following properties:

Matrices can be either numeric or character. Elements of a numeric matrix are stored in double precision. Elements of a character matrix are character strings of equal length. The length can range from 1 to 32676 characters.
Matrices are referred to by valid SAS names. Names can be from 1 to 8 characters long, beginning with a letter or underscore, and continuing with letters, numbers, and underscores.
Matrices have dimension defined by the number of rows and columns.
Matrices can contain elements that have missing values (see the section "Missing Values" later in this chapter).

The dimension of a matrix is defined by the number of rows and columns it has. An m ×n matrix has mn elements arranged in m rows and n columns. The following nomenclature is standard in this book:

1 ×n matrices are called row vectors.
m ×1 matrices are called column vectors.
1 ×1 matrices are called scalars.

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