Line chart | the R Graph Gallery

Note on line chart

This section is tightly linked with other sections. A connected scatterplot is almost the same thing, but each observation is represented as a dot. An area chart fills the surface between the line and the X axis. More generally, the time series section can interest you.

connected scatter area chart time series

Step by step with ggplot2

ggplot2 allows to draw line charts thanks to the geom_line() function. It expects as input a data frame with 2 numeric variables, one displayed on each axis. Start your journey with the most basic line chart.

Most basic

Most basic line chart with R and ggplot2

Basic customization

Basic customization to improve the line chart: size, color, type, theme, title and more

Log transform

How to use a log transformation for the Y axis with scale_x_log10().

Deal with date

How to avoid struggling with dates on the X axis

Basic Grouped line chart

How to build a line chart representing several groups

Customized Grouped

Pick up a nice color palette, use a theme, add titles, and more.

Linear trend

geom_smooth allows to add the result of a model to your scatterplot, with confidence interval as well.

Annotation

Annotation allows to highlight main features of a chart. Learn how to add text, circles, lines and more.

Dual Y axis

A few examples showing how to use the sec.axis argument to add a second Y axis.

geom_ribbon and geom_smooth

Line charts are often displayed together with confidence intervals. ggplot2 offers 2 main functions to build them. geom_ribbon allows to build the area around the curve from precomputed values. geom_smooth will compute a model for you and plot the result directly.

Geom_smooth()

geom_smooth allows to add the result of a model to your scatterplot, with confidence interval as well.

Geom_ribbon()

If you already know the upper and lower limits of the error envelop, geom_ribbon will plot it for you.

Mind the Spaghetti (ggplot2)

When too many groups are displayed on the same line chart it gets very hard to get insight from the figure. This is commonly called a spaghetti chart. Here are a few alternatives using ggplot2: annotation and small multiple.

Spaghetti chart

Too many lines with 10+ legend entries? You are building a spaghetti chart and readers will struggle to get info from it.

Annotation

Try to understand what really matters, highlight it and annotate it to make sure people get your point.

Small multiple

Split the layout: each group having its own space. It makes it easier to understand what's happening for each them.

Step by step with base R

In base R, the line function allows to build quality line charts.

Line color and Y value

Change the line color according to the Y axis value

How to add a legend to base R plot

The legend() function allows to add a legend. See how to use it with a list of available customization.

Reversed Y axis

Learn how to flip the Y axis upside down using the ylim argument.

Polynomial curve

Line charts are often used to represent the result of a statistical model.

Parameters reminder

A cheatsheet to quickly reminder what option to use with what value to customize your chart.

Dual Y axis with ggplot2

Warning: a dual Y axis line chart represents the evolution of 2 series, each plotted according to its own Y scale. This kind of chart must be avoided, since playing with Y axis limits can lead to completely different conclusions. Visit data-to-viz for more info.

Why you should avoid it

Most basic dual Axis

Most basic usage of sec.axis attribute to display a second Y axis.

More style

Customize the chart style with title, colors, theme and more.

Mix geoms

A dual axis chart mixing a line chart with a barplot.

Dual Y axis with latticeExtra

Why you should avoid it

Line chart with 2 series

A classic line chart with 2 series, only 1 Y axis.

Dual Y axis line chart

Add a second Y axis for the second sery. See how chart conclusion gets different and wrong.

Add legend

Add a legend to specify what color is linked to what value.