Displayed vs Run-In
21.2 Displayed vs Run-In
Simple formulas may remain within the text of the manuscript if they can be set on the line:
The pulmonary vascular resistance index (PVRI) was calculated as follows: PVRI = (MPAP − PCWP)/CI, where MPAP indicates mean pulmonary artery pressure; PCWP, pulmonary capillary wedge pressure; and CI, cardiac index.
Long or complicated formulas should be centered on a separate line. In either case, symbols and signs should be marked in detail. Such formulas may be handled either as copy or as prepared art, depending on the availability of special characters and use of software for equation preparation. For online publications, formulas that require more than 1 line must either be shown as an image or depicted by means of specialized mathematical software.
Whether run into the text or centered, an equation is an element of the sentence that contains it. Punctuation and grammatical rules thus apply to it, just as they do to all other sentence elements. For example, if the equation is the last element in a sentence, it must be followed by a period. If there are 3 equations in a list, they must be separated by commas and the final equation must be preceded by “and.”
If there are numerous equations in a manuscript, or if equations are related to each other or are referred to after initial presentation, they should be numbered consecutively. Numbered equations should each be set on a separate line, centered, with the parenthetical numbers set flush left.
x = r cosθ
y = r sinθ
z = (x+y)
Standard abbreviations should be used in expressing units of measure (see 14.12, Abbreviations, Units of Measure). For short, simple equations, it may be preferable to express an equation as words in the running text, rather than to set it off as an actual formula:
Attributable risk is calculated by subtracting the incidence among the nonexposed from the incidence among the exposed.