numrows

NumRows is a common variable name used in programming and data processing to denote the number of rows in a two-dimensional structure such as a matrix, table, or grid. It is not a built-in function, but a conventional identifier chosen by developers to keep code readable. The value of numRows typically equals the count of items along the vertical dimension.

In Python, for a 2D list called matrix, numRows is often set to len(matrix). In Java, for a 2D array, numRows is matrix.length, and numCols is matrix[0].length when all rows have the same length. In R, the number of rows in a data frame or matrix is given by nrow(object), often assigned as numRows <- nrow(df). In SQL or data-processing contexts, the size is usually obtained by a count operation such as SELECT COUNT(*) and stored in a variable named numRows for subsequent logic.

In user interface contexts, numRows may control the height of a grid or table, or influence pagination and rendering. In data pipelines, numRows can determine iteration counts or how to partition work across tasks.

Common pitfalls include zero rows, ragged structures where rows have varying lengths, and negative values being invalid in many contexts. Some languages treat the row count as read-only, while others require updates if the underlying data changes. It is often best to derive numRows from the actual data when possible to avoid mismatches.

Related terms include rowCount and height, and in databases the concept often aligns with the number of records in a table.