> For the complete documentation index, see [llms.txt](https://vikram-bajaj.gitbook.io/cs-gy-6313-information-visualization/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://vikram-bajaj.gitbook.io/cs-gy-6313-information-visualization/graphical-components-and-mapping-strategies/contextual-components.md).

# Contextual Components

Apart from marks and channels, we also have other important graphical elements. These are referred to as contextual components. There are 2 categories:

* legends, labels and annotations
* axes, grids and reference lines

## Legends, Labels and Annotations

Legends and labels enable the **interpretation** of the graphical elements.

Annotations guide attention to and explain patterns of interest.

## Axes, Grids and Reference Lines

These components enable **value reading** and **comparisons**.

A **Trend Line** can be used to depict the overall trend in the data. We can also use the trend line to which determine values lie above and below it.

![](https://612062878-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M5-0RG_uqhxyMNjpMUW%2F-M5-0SvQ45Rarxg8L2lA%2F-M5-0TvDEdNrQ9pAnYwB%2Ftrend%20line.PNG?generation=1586990816140176\&alt=media)

In the graph shown above, the dashed line is the trend line.

Other reference lines can be used to set thresholds, and thereby to categorize quantitative values. Ex. to give letters to restaurant evaluation scores.