Cover Every Data Point

Two kinds of position MUST still be covered:

• A labeled position with no mark is a data point whose value is 0 — the histogram's empty 1500 bin is 0 (see Bars and Histograms (§11.2.1)).
• A position the axis does not label is located by its axis value: 2023 on a year axis that ticks every third year, 2500 on a bin axis that labels every other bin. The printed, regularly labeled axis is the calibration; a position that no printed calibration reaches is not locatable.

The default is in. A data point that can be read MAY be left out only when:

• no printed text can uniquely locate it — see Labels (§11.1.2); the unnamed companion curve in Legend and Overlay Values (§11.2.4) is the standing example; or
• it is genuinely unreadable — too blurred, too dense, or overlapping beyond judgment.

Leaving a point out MUST NOT be replaced by invented text: a made-up series name, a made-up category or a placeholder cell stands for nothing on the page (see Never Drop, Never Invent (§2.2)).

Values are read from the page. A value MUST NOT be shaded towards what some parser or earlier rendering produced, and a correct value stays correct however many renderings disagree with it (see The Page Is the Ground Truth (§2.1)).

Every table representing a chart MUST open with <table data-source="chart">. The data-source="chart" attribute belongs on the opening <table> tag, including when the chart prints a data grid that supplies the table's content (see Chart With a Printed Data Grid (§9.1.2)). A table representing an ordinary printed table MUST NOT carry data-source="chart".

The layout of the chart table. A chart table MUST be laid out as follows, so that every chart table reads the same way — category down, series across:

• one HTML <table data-source="chart"> per chart or panel, at the chart's place in reading order;
• the chart's title, subtitle or caption in <caption> inside that table, first or last according to reading order (see Titles Banners Captions (§9.7.3)); its printed notes and source follow the table;
• one row per category position (axis tick, bar, bin, slice, tile, region, named point), in the order the axis runs — left to right, top to bottom, a pie clockwise from the top;
• a first column holding the category labels, then one column per series in legend order;
• a header row holding the printed series names, its first cell holding the printed category-axis title or left empty; a single series with no printed name is headed by the printed value-axis title; when nothing printed names any column, the table has no header row;
• a printed total that is not itself a category (a stack total above its bar) sits in a last column under an empty header cell;
• printed text of the chart that is not a data point — axis titles not used as headers, unit notes, reference-line labels, event callouts, annotation boxes, legend entries of series that carry no value — follows the table as plain text in reading order.

The value in each cell is governed by Values and Tolerances (§11.1.4); the labels in the first column and the header row by Labels (§11.1.2).