nCols

ncols is a parameter used in software libraries to specify the number of columns in a grid layout. It denotes how many columns of items, such as subplots, images, or widgets, should appear in a single row. The value is typically a positive integer and is often paired with a corresponding nrows parameter or a layout specification.

In plotting and visualization, ncols determines the horizontal arrangement of panels. It is commonly used together with nrows to form a grid of subplots. For example, when creating multiple plots, a grid of nrows by ncols may be allocated, and each subplot is placed in the grid in a defined order. Some libraries also allow providing only ncols, in which case the number of rows may be inferred from the total number of plots or derived from a layout setting.

In practice, the exact behavior of ncols depends on the library. Matplotlib, for instance, uses separate nrows and ncols arguments to plt.subplots, while other wrappers or higher-level interfaces may accept a layout or automatically compute the grid from the specified ncols. The concept also appears in other contexts, such as arranging multiple images in a mosaic or organizing UI elements into a grid.

Common considerations include ensuring ncols is at least 1, understanding how empty grid cells are handled if the number of items is not a multiple of ncols, and recognizing how nrows interacts with ncols to determine the total grid size. See also nrows.