Halfplot

Halfplot is a term used in data visualization to describe a plot that emphasizes half of a dataset or a half of a distribution in a single frame. In its common form, the graphic presents either the upper or lower portion of a distribution, or the positive or negative half of a variable, with the alternate half omitted or depicted only as a reference. The technique highlights magnitude and asymmetry, reducing clutter when symmetry is assumed or uninformative.

Construction involves selecting a halving rule: by value (upper vs lower tail), by order (first half vs second half), or by sign (positive vs negative). The chosen half is drawn using standard plotting scales; the other half may be omitted, mirrored, or rendered with diminished emphasis. The method can be applied to histograms, density plots, line plots, or scatter plots.

Applications include exploratory data analysis, where the goal is to assess skewness or compare halves of a distribution; and communication, where a single panel can contrast two regimes without duplicating plots. Examples: comparing gains and losses in financial returns, or contrasting seasonal extremes within a single frame.

Advantages include concise representation of asymmetry and efficient use of space. Limitations include potential misinterpretation due to the omitted data, reliance on careful labeling, and the risk of obscuring the full distribution.

See also: data visualization, mirror plot, split violin plot.