Understanding Error Bars in Grapher

Error bars are essential components of scientific and engineering graphs, providing critical context for interpreting visualized data. They decipher the precision and variability of data measurements, transforming a plot from a collection of graphical elements into a powerful tool for communicating data reliability. This guide explains how to effectively add and customize error bars in Grapher, enabling you to create accurate and informative representations of your scientific and engineering data.

Error bars can be displayed on line plots, scatter plots, line/scatter plots, horizontal bar charts, vertical bar charts, 3D ribbon plots, 3D wall plots, 3D horizontal bar charts, and 3D vertical bar charts.

Error bar types

You can set the error bar type in the Properties Manager's Error Bar tab. The ideal choice depends on the specific insights you want to convey about your data's distribution and variability. Options for calculating error bars include using pre-calculated values from a data variable (the only method for simultaneous vertical and horizontal error bars), the average value only for central tendency, sample standard deviation for variability within a data sample, or population standard deviation for entire datasets. Additionally, you can select the standard error of the mean to show the precision of the mean as an estimate of the true population mean.

Add error bars to a plot in Grapher

To accurately represent the variability and precision of your data, adding error bars to your plots in Grapher is crucial. This section will guide you through the straightforward process of incorporating error bars into your visualizations, enhancing their scientific integrity. Follow these steps to add error bars to a plot:

1. In the Object Manager, select your plot.
2. In the Property Manager, click the Error Bars tab.
3. Change the Direction field to Vertical, Horizontal, or Vertical and Horizontal.
4. Set the error bar properties in the General section. If you have selected Vertical and Horizontal, the properties being displayed in the General section are for the direction selected in the Properties to edit field.

Line Scatter plot with positive and negative error bars.

Connect error bars and fill between them

Beyond simply displaying error bars, Grapher allows you to connect them and fill the area between, creating a powerful visual representation of data uncertainty or confidence intervals. This section will walk you through the steps to achieve this, providing a clearer and more informative visualization of your data's spread

1. Select your line plot.
2. In the Property Manager, select the Error Bars tab.
3. In the Direction field set the desired direction of your error bars, and then set the type of error bar.
4. Once your error bars are displaying, check the box next to the Connect points field.
5. In the Property Manager, select the Line tab.
6. In the Error Bar Line Properties section expand the appropriate Connection Line section, such as Error Bars or Vertical Error Bar Connection Line, and edit the line properties.
7. In the Property Manager, select the Fill tab.
8. Expand the appropriate error bar fill section, such as Vertical Error Bar Connection Fill, and edit the fill properties.

Line Scatter plot with displaying fill between connected error bars.

Only show the fill between the error bars / Error Bands

For a streamlined visual that emphasizes data uncertainty without individual error bar lines, Grapher enables you to display only the fill between error bars, often referred to as "error bands." This section details how to create these impactful error bands, providing a clear visual representation of data variation.

1. Follow the step in the Connect error bars and fill between them section above.
2. In the the Property Manager, select the Error Bars tab.
3. In the Error Bars section, set the Cap width field to zero.
4. In the the Property Manager, select the Line tab.
5. In the Error Bar Line Properties section, in the Error Bars section, set the Style field to Invisible.
6. In the Error Bar Line Properties section, in the Vertical Error Bar Connection Line section, set the Style field to Invisible.
7. In the the Property Manager, select the Fill tab.
8. In the Plot Fill Properties section, in the Vertical Error Bar Connection Line section, set the Pattern field to Solid.
9. In the Plot Fill Properties section, in the Vertical Error Bar Connection Line section, set the Color field to Solid to your desired color.

Dive Deeper : Error Bar Resources and Customization

The customizations showcased on this page are just a subset of what's possible with error bars. For comprehensive details on adjusting their appearance and settings, please refer to the Grapher Help entries on Error Bars and Error Bar - Line Properties.