The standardized gtable representation ensures that all plots share a consistent row–column structure, facilitating flexible composition, patch insertion, and alignment across multiple plots.
This layout provides a fixed-size gtable grid for predictable positioning of plot components such as titles, axes, legends, captions, and margins. It is used internally for layout normalization and patch-based alignment.
Row structure (top -> bottom)
| Index | Component | Description |
| 1 | margin-top | External top spacing |
| 2 | tag-top | Top tag (e.g., "A", "B") |
| 3 | title | Main title |
| 4 | subtitle | Subtitle |
| 5 | guide-box-top | Legend box at top |
| 6 | legend.box.spacing | Space between legend and main area |
| 7 | patch-title-top | Top patch title |
| 8 | xlab-top | Top x-axis label (rare) |
| 9 | axis-top | Top axis ticks and labels |
| 10 | strip-top | Top strip (facet label) |
| 11 | panel | Main plotting panel |
| 12 | strip-bottom | Bottom strip (facet label) |
| 13 | axis-bottom | Bottom axis ticks and labels |
| 14 | xlab-bottom | Bottom x-axis label |
| 15 | patch-title-bottom | Top patch title |
| 16 | legend.box.spacing | Space before bottom legend box |
| 17 | guide-box-bottom | Bottom legend box |
| 18 | caption | Caption or footnote text |
| 19 | tag-bottom | Bottom tag (optional) |
| 20 | margin-bottom | External bottom spacing |
Column structure (left -> right)
| Index | Component | Description |
| 1 | margin-left | External left spacing |
| 2 | tag-left | Optional side tag |
| 3 | guide-box-left | Left legend box |
| 4 | legend.box.spacing | Space between legend and panel |
| 5 | patch-title-left | Left patch title |
| 6 | ylab-left | Left y-axis label |
| 7 | axis-left | Left axis ticks and labels |
| 8 | strip-left | Left strip (facet label) |
| 9 | panel | Main panel area |
| 10 | strip-right | Right strip (facet label) |
| 11 | axis-right | Right axis ticks and labels |
| 12 | ylab-right | Right y-axis label |
| 13 | patch-title-right | Right patch title |
| 14 | legend.box.spacing | Space before right legend box |
| 15 | guide-box-right | Right legend box |
| 16 | tag-right | Optional tag on right side |
| 17 | margin-right | External right spacing |