Categories

Categories identify discrete positions such as quarters, regions, or product names. Use associative arrays so each value carries its label.

Shared order

The first call to series() defines the category labels and their order. Every later series must provide the same keys in the same order.

$model = Chart::bar()
    ->series('2025', ['Q1' => 18, 'Q2' => 32, 'Q3' => 24])
    ->series('2026', ['Q1' => 26, 'Q2' => 24, 'Q3' => 38])
    ->build();

This mismatch is rejected even though it contains the same labels:

Chart::bar()
    ->series('2025', ['Q1' => 18, 'Q2' => 32])
    ->series('2026', ['Q2' => 24, 'Q1' => 26]);

Stable ordering keeps each value attached to the intended visual position. Category labels must also be unique and non-empty.

Values

Category values must be finite integers or floats. Grouped bar, line, and area charts accept positive and negative values. Stacked bars require non-negative values because each segment contributes to a total.

Radar charts also require non-negative values and at least three categories. The renderer places categories around the radial frame in insertion order.

Positioning

The renderer divides the available plot into equal category bands. Labels and marks are centered within those bands automatically. There is no public API for individual category positions or label alignment.