matrixGetLength1

matrixGetLength1 is a function used in some numerical computing libraries to obtain the size of the first dimension of a matrix or array. It is commonly applied to two-dimensional matrices to determine the number of rows, but the function is defined for higher-dimensional arrays as well.

In typical implementations, matrixGetLength1 returns the extent of the first axis. For a rank-2 matrix, this corresponds to the number of rows. For higher-rank arrays, it returns the size of the first dimension (the length of the outermost axis). The function assumes the input is array-like; behavior for non-array inputs usually involves raising an error. In the case of irregular or jagged arrays, the result reflects the length of the outermost dimension rather than any inner dimensions.

The return value is an integer representing the size of the first dimension. Access is typically O(1) since the first-dimension length is stored as metadata in well-designed array structures. Some languages or libraries may also provide alternative means to obtain dimension information, such as a general size or shape function, but matrixGetLength1 focuses specifically on the first axis.

Examples help illustrate its use. For a matrix A with shape (3, 4), matrixGetLength1(A) yields 3. For a higher-dimensional array with shape (5, 3, 2), matrixGetLength1(array) yields 5. Users should consult the specific library’s documentation for exact behavior on edge cases and error handling.

See also: matrixGetLength2 for the second dimension, size or Dimensions for general shape queries.