group, datum

<group> and <datum> are containers created by groups and repeat, respectively. They rarely need to be created manually. The Variance structural CSS uses these elements position data according to the numeric scales (or responsively via CSS flexbox, for directions that are not explicitly mapped to numeric data dimensions).

Every <group> tag will have in scope data (corresponding to the data subset) and group (the value of the grouping key for that subgroup).

Every <datum> tag will have in scope the properties of the underlying datum (i.e., a “row” of the data; a <datum> within a <repeat> over student test scores might have in scope student: "Ryan" and score: 89).