geom_segment

---

Draws a straight line between point coordinates (x, y) and (xend, yend).

Aesthetics

Other Properties

Similar Geometries

geom_curve, geom_path, geom_line

Description and Details

Using the described geometry, you can insert a simple geometric object into your data visualization – a line segments layers that is defined by a position aesthetic properties x, y, xend and yend. You can find this geometry in the ribbon toolbar tab Layers, under the Primitives button.

Geometry layer geom_segment is used to create line segments that are positionally defined by the initial (x, y) and the final coordinate (xend, yend). The following figure shows a very simple example. We used a selection from the built-in iris dataset. As the starting points we use Sepal_Length (x-axis) and Sepal_Width (y-axis) variables. We used the same variables to define endpoints, which we moved to a constant value (1). The result is shown in the following figure.

The program has generated several simple lines according to defined parameters. Using the other aesthetics properties, you can change the visual character of line segments. These parameters can be set or mapped to selected variables from the dataset. The following figure shows an example of a line thickness (size aes) and line end settings.

In the Properties section, you find one specific parameter named arrow. Using this property, you can define the arrow head at the beginning or end of each line segment. This property is defined as the R function – arrow() with multiple arguments. The dialog for setting these arguments can be found in the context menu under the Define… item.

In this dialog you can set the arrow head angle, length, type and also you can define whether the arrow head will be placed at the beginning or end of the line segment.

An example of line segments with arrow heads is shown in the following plot.

Using the described geometry, you can create relatively impressive data visualizations. The example is shown in the following data visualization. In this case, we have created a large number of line segments, which are defined by the start coordinate (lat, long) and with shifted end coordinate (lat + delta_lat, long + delta_long). The color aesthetic property we mapped to a function that is based on the delta_lat * delta_long variables. Similar visualizations are often used in the field of environmental sciences or geosciences. A similar type of visualization (defined differently) can be created using geom_spoke geometry.