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Error Bars

In this tutorial, you’ll learn how to draw an Error Bars in Glimpse. You can use it to indicate an estimated error or uncertainty. You can also give a general sense of how precise a measurement is. Error bars can be used to display the standard deviation, standard error, confidence intervals, or interquartile range.

In this example, we will be applying Error Bars to a Dot Graph. However, you can also apply Error Bars to other marks, such as: Bar, Shape, Square, Line, etc.

Start by adding data from a sample JSON file. Go to the top menu and choose Data > Sample Data > and select the barley.json file.

Then, under Visual > Mark in the Inspector panel to the right side of the UI, set the Mark Type to Circle.

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From the left side of the UI, drag the yield field into the X encoding. Then, go to the Inspector panel and set the Aggregate to Average.

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Now, drag the variety field into the Y encoding.

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Let’s set the error bars now. From the top menu, choose Insert > Layer > Error Bar, and drag the fields yield into the X encoding and variety into the Y encoding.

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To set the extent of the rule, go to the Inspector panel*, open **Visual > Mark > Extent and choose Standard Deviation from the dropdown.

In this place of the app, you can set the Error Bars to be based on:

Standard Deviation (the default), Confidence Interval, Standard Error, Q1-Q3 which is the interquartile range from the first quartile to the third quartile.

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Now, expand the Ticks section below and set the Color to black to display the end ticks. The Black color is in the Grey Hues color pallette - you will need to scroll down a bit to find it.

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Done! This is how you draw Error Bars in Glimpse. If you want to further customize your chart, please read the documentation.