Customizing Tooltips for Multiple Y-Axes in R with Highcharter

Overview

Highcharter is a popular R package used to create interactive charts. One of its powerful features is the ability to customize tooltips, which provide additional information about each data point on the chart. In this article, we will explore how to customize tooltips for multiple y-axes in Highcharter.

In the example provided in the question, two y-axes are created: one for value and one for percentage. The user wants to display a different format for the tooltip point values depending on which series is being displayed. We will delve into the details of how to achieve this customization.

Understanding Highcharter’s Tooltip Mechanics

Highcharter’s tooltips are created using the hc_tooltip() function, which accepts an optional list argument that contains various options to customize its behavior. The most relevant option for our purpose is pointFormat, which specifies the format in which data points will be displayed.

Problem with Default pointFormat

The default pointFormat provided by Highcharter does not accommodate multiple y-axes or conditional formatting based on series names. When trying to apply the suggested solution using hc_tooltip(list(pointFormat = "...")), it doesn’t work as expected because Highcharter expects a single format string that applies uniformly across all data points.

Solution: Conditional Formatting for Multiple Y-Axes

The provided answer reveals an elegant way to handle this situation by applying individual tooltip settings to each series. By doing so, we can explicitly specify the format for the point values based on their respective y-axis and series names.

Setting Up Highcharter with Custom Tooltip Formats

highchart() %>% 
  hc_yAxis_multiples(list(title=list(text="<b>Value</b>"),
                          showLastLabel = FALSE,opposite = FALSE),
                     list(title=list(text="<b>Percent</b>"),
                          showLastLabel = FALSE, opposite = T)) %>% 
  hc_add_series(c(seq(100,110)), yAxis=0,
                tooltip = list(pointFormat = "&lt;b&gt;{series.name}: ${point.y:,.0f}")) %>% 
  hc_add_series(c(seq(1,10)), yAxis=1,
                tooltip = list(pointFormat = "&lt;b&gt;{series.name}: {point.y:,.2f}%"))

Key Takeaways

• To customize tooltips for multiple y-axes in Highcharter, apply an individual tooltip setting to each series using the hc_add_series() function.
• In the tooltip list, use the pointFormat option to specify the desired format string. This can include variables like {series.name} and ${point.y:,.0f} (for integer values) or {point.y:,.2f}% (for decimal percentages).

Customizing Point Formats for Multiple Y-Axes

Highcharter allows you to further customize the point formats by utilizing various R built-ins, such as format() from the printf() family. We can leverage these functions to create more sophisticated and informative format strings.

Examples of Customized Point Formats

highchart() %>% 
  hc_yAxis_multiples(list(title=list(text="<b>Value</b>"),
                          showLastLabel = FALSE,opposite = FALSE),
                     list(title=list(text="<b>Percent</b>"),
                          showLastLabel = FALSE, opposite = T)) %>% 
  hc_add_series(c(seq(100,110)), yAxis=0,
                tooltip = list(pointFormat = "&lt;b&gt;{series.name}: {printf(\\${point.y} \\%d\\.2f')}")) %>% 
  hc_add_series(c(seq(1,10)), yAxis=1,
                tooltip = list(pointFormat = "&lt;b&gt;{series.name}: {printf(\\${point.y} \\%)}"))

Explanation of Customized Format Strings

• The printf() function within the format string is used to generate a string with a specified number of decimal places.
• For integer values, we use {printf(${point.y} %d.2f)} to display two decimal places. If the value contains an implicit decimal point (e.g., .99), this will still produce two digits after the decimal point.

Conclusion

Customizing tooltips in Highcharter can be achieved by utilizing conditional formatting, specifically within each individual series’ tooltip settings. By combining various R functions like printf() and applying a well-crafted format string, we can effectively create informative and user-friendly tooltips for multiple y-axes in our charts.

Further Exploration

For more complex charting scenarios or exploring additional features of Highcharter, you might want to consider the following:

• Series Grouping: Using hc_add_series() with a grouping argument (group).
• Data Series Color Cycles: Utilizing hc_add_series() with a color cycle configuration.
• Multi-Series Line and Bar Charts: Creating line or bar charts that display multiple series on the same chart.

These capabilities will expand your chart customization options, enabling you to further enhance data visualization in R using Highcharter.

Last modified on 2023-07-09