Deep-dive blogpost about ggplot2 themes #745
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thomasp85
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| In addition to these elements in ggplot2, extension packages can also define custom elements. | ||
| Generally speaking, these elements are variants of the elements listed above and often have slightly different properties and are rendered differently. | ||
| For example `ggtext::element_markdown()` is a subclass of `element_text()`, but interprets the provided text as markdown. | ||
| It applies some html tags like `<b>` for bold and `<i>` for italic when rendering the text. | ||
| Another example is `ggh4x::element_part_rect()` that can draw a subset of rectangle borders. | ||
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| ```{r element_markdown} | ||
| p + | ||
| labs(title = "<b>Fuel</b> <i>efficiency</i>") + | ||
| theme( | ||
| plot.title = ggtext::element_markdown(), | ||
| strip.background = ggh4x::element_part_rect(colour = "black", side = "b") | ||
| ) | ||
| ``` |
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Use marquee to avoid recommending a package we consider superseded
| Travelling from roots to leaves, properties of theme elements are inherited from parent to child. | ||
| Some inheritance is very direct, where leaves directly inherit from roots (for example `legend.text`). | ||
| Other times, inheritance is more arduous, like for `axis.minor.ticks.y.left`: it inherits from `axis.ticks.y.left`, which inherits from `axis.ticks.y`, which inherits from `axis.ticks`, which finally inherits from `line`. | ||
| Most often, elements only have a single parent, but there are exceptions so the inheritance of theme elements is not strictly a directed acyclic graph. |
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This is not really true. A DAG can have multiple inheritance as long as it is not cyclic. So the theme is a DAG but not a tree
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| The `?theme` documentation often tells you how the elements inherit and `calc_element()` will resolve it for you. | ||
| If, for some reason, you need programmatic access to the inheritance tree, you can use `get_element_tree()`. | ||
| Let's say you want to find out exactly why theme inheritance is not a directed acyclic graph. |
| text = element_text(margin = margin(l = 6, unit = "mm")), | ||
| margin = margin(l = 6, unit = "mm") | ||
| ) | ||
| ``` |
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Maybe mention here how you can make the bar stretch the full height/width of the plot
| } | ||
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| p + my_theme() | ||
| ``` |
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Maybe mention the requirement to use system fonts-compatible graphics devices?
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As discussed with @thomasp85, this blogpost is intended as a deep-dive into ggplot2 styling, covering much of
theme()including new functionality.