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This article is about Looker Studio. For Looker documentation, visit https://cloud.google.com/looker/docs/intro.

Add reference lines and reference bands to charts

Highlight values and ranges of interest in your charts and visualize progress towards your goals.

Reference lines and reference bands display how the data in a chart compares against a preset value. For example, you can use  reference lines to visualize how daily sales compare to a target sales figure, or to compare the average sale data for individual stores against a regional sales average.

In this article:

Reference lines and reference bands in Looker Studio

There are two types of reference lines that can be added to charts:

  • Reference line 

    A reference line is helpful for highlighting a single value to compare data against.

    You can also choose to highlight a date along the X-axis in the Axis section of the Style tab.
     
  • Reference band 

    A reference band is another type of reference line that is helpful for comparing data against a range of values. For example, you can highlight whether data is in a favorable or unfavorable range with a reference band. 

    You can also choose to highlight date ranges along the X-axis in the Axis section of the Style tab.

Reference line and reference band examples

You can use a reference line to highlight a single value, such as a sales goal, to compare data against. For example, you can use a reference line to highlight a Weekly sales target in a time series chart that displays Sales by Date

A Weekly sales vs. target time series chart displays a Weekly sales target horizontal reference line.

You can use a reference band to highlight a set range against which to compare data. For example, you can highlight a Mobile subscription sales goal range in a time series chart that displays Mobile Subscriptions by Year

A time series chart displays mobile subscriptions by year with a reference band that highlights the Mobile subscription sales goal range of 3 billion to 5 billion.

Reference lines versus trend lines

Reference lines let you show target values and set thresholds and benchmarks so you can see how your data matches expectations or goals.

Trend lines reveal the overall direction of the data in a chart. Trend lines can help you see patterns and make predictions from otherwise random-appearing data. In Looker Studio, you can add trend lines to time series and scatter charts.

Add a reference line or reference band

You can add reference lines to time series, line and combo charts, bar and column charts, area charts, and scatter charts.

  1. Edit your report.
  2. Select a chart.
  3. In the right-hand Properties Panel, select the Style tab.
  4. Click Add a reference line or Add a reference band.
  5. Configure the reference line or reference band using the options outlined in the Reference line style options and Reference band style options sections on this page.

You can add up to 10 reference lines per chart.

Reference lines and reference bands appear with either a default label, or a custom label that you apply.

You can hover your cursor over a reference line or reference band to access a tooltip that displays more details about the reference values.

Reference line style options

Configure a reference line using the following options on the Style tab of the right-hand Properties Panel

Type

Determines the value upon which the reference line is based.

Constant value

Base the reference line on a value that you type in. For example, if your sales target is $10,000 per day, enter 10000. For a percentage value, enter the number as a decimal (.5 equals 50%).

Metric

Base the reference line on a metric that appears in the chart.

Parameter

Base the reference line on a parameter that you select. Only single-valued numeric parameters are allowed.

Calculation

For metric-based reference lines, choose the aggregation to apply to the selected metric. For example, if the chart is visualizing Users by Week, you can create a reference line showing the average number of weekly users by choosing the Users metric and Average calculation.

Available calculations:

  • Average
  • Median
  • Percentile - Enter the percentile as a whole number between 0 and 100.
  • Min
  • Max
  • Total

Axis

Display the reference line on the chart's X, Y, Left-Y, or Right-Y axis. This option applies to constant value and parameter-based reference lines. The available axes depend on the chart type.

If you select x-axis and your x-axis is a date dimension, a date selector will appear that lets you specify a date to highlight as a reference on the chart.

Label

Display a custom label for the reference line.

If you leave the Label field blank, Looker Studio supplies a default label. For constant value reference lines, the label is Reference Line #n. For metric reference lines, the default label is the type of calculation that is applied. For parameter reference lines, the default label is the parameter name.

Click the Show label checkbox to display the label on the chart by default. Clear the Show label checkbox to hide the label from the chart.

Show reference value in label

When you click the Show label checkbox, the option to Show reference value in label also becomes available. 

Click the Show reference value in label checkbox to display the reference line value. The value will be appended to the label. 

Line weight

Select a number from the Line weight drop-down menu to change the thickness of the reference line. The higher the number that you select, the thicker the line will appear. 

Line style

Select an option from the Line style drop-down to change the appearance of the reference line. Using different line styles can be helpful in distinguishing between multiple lines that appear in a chart. 

Line style options include the following:

  • Dashed
  • Dotted
  • Solid
  • Dash-dot
  • Long dash
  • Long dash-dot

Line color

Use the Line color color selector to change the color of the reference line. 

Reference band style options

Configure a reference band using the following options on the Style tab of the right-hand Properties Panel

Beginning value

These settings determine the starting value of the reference band range.

Type

Select the type of value to begin the reference band range.

You can have different Type options selected for the Beginning value and the Ending value. For example, you can use an Average calculation for the starting value, and a Metric value for the ending value, depending on which value is greater.

Constant value

Base the reference band beginning value on a number that you type in. For example, if your sales target is $10,000 per day, enter 10000. For a percentage value, enter the number as a decimal (.5 equals 50%).

Metric

Base the beginning value of the reference band on a metric that appears in the chart.

Parameter

Base the beginning value of the reference band on a parameter that you select. Only single-valued numeric parameters are allowed.

Calculation

For metric-based beginning values, choose the aggregation to apply to the selected metric. 

The available calculations are as follows:

  • Average
  • Median
  • Percentile - Enter the percentile as a whole number between 0 and 100.
  • Min
  • Max
  • Total

Label

Display a custom label for the reference band.

If you leave the Label field blank, Looker Studio supplies a default label. For constant value reference bands, the label displays the range of the band. For metric reference bands, the default label is the type of calculation that is applied. For parameter reference bands, the default label is the parameter name.

Click the Show label checkbox to display the label on the chart by default. Clear the Show label checkbox to hide the label from the chart.

Show reference value in label

When you click the Show label checkbox, the option to Show reference value in label also becomes available. 

Click the Show reference value in label checkbox to display the reference band value.

The value will be appended to the label and will be display the band range as the lowest value to highest value. For example, for a reference band with a low value of 3,000 and a high value of 5,000, the value will be displayed as 3,000 to 5,000.

Line weight

Select a number from the Line weight drop-down menu to change the thickness of the reference band lines. The higher the number that you select, the thicker the line will appear. 

Line style

Select an option from the Line style drop-down to change the appearance of the reference band lines. Using different line styles in distinguishing the line from other lines that appear in a chart. 

Line style options include the following:

  • Dashed
  • Dotted
  • Solid
  • Dash-dot
  • Long dash
  • Long dash-dot

Background color

Use the Background color selector to select a fill color for the area between the Beginning value and the Ending value range.

Line color

Use the Line color color selector to change the color of the reference band lines. 

Opacity

Select a value from the Opacity drop-down menu to change the opacity of the fill color. The higher the percentage that you select, the less opaque the fill color will appear. 

Ending value

These settings determine the starting value of the reference band range.

Type

Select the type of value to end the reference band range.

You can have different Type options selected for the Beginning value and the Ending value. For example, you can use an Average calculation for the starting value, and a Metric value for the ending value, depending on which value is greater.

Constant value

Base the reference band ending value on a number that you type in. For example, if your sales target is $10,000 per day, enter 10000. For a percentage value, enter the number as a decimal (.5 equals 50%). 

Metric

Base the ending value of the reference band on a metric that appears in the chart.

Parameter

Base the ending value of the reference band on a parameter that you select. Only single-valued numeric parameters are allowed.

Calculation

For metric-based ending values, choose the aggregation to apply to the selected metric. 

The available calculations are as follows:

  • Average
  • Median
  • Percentile - Enter the percentile as a whole number between 0 and 100.
  • Min
  • Max
  • Total

Axis

Display the reference band on the chart's X, Y, Left-Y, or Right-Y axis. This option applies to constant value and parameter-based reference bands. The available axes depend on the chart type.

If you select x-axis and your x-axis is a date dimension, a date selector will appear in the Beginning value  and Ending value sections that lets you specify a date range to highlight  on the chart.

Remove a reference line or reference band

To remove a reference line from a chart:

  1. Edit your report.
  2. Select the chart.
  3. In the right-hand Properties Panel, select the Style tab.
  4. Locate the reference line or reference band that you want to remove, then click the Delete reference line or Delete reference band icon Delete icon..

Edit charts with reference lines or reference bands

If you change the chart type, Looker Studio deletes any reference lines or reference bands that are not supported by the new chart type.

If you remove a metric from the chart, Looker Studio deletes any reference lines or reference bands that are associated with that metric.

Limits of reference lines

  • Reference lines are only available for numeric axes. Reference lines on date axes aren't supported.
  • Metric-based reference lines can only consider values currently displayed in the chart. For example, if you add a reference line to a bar chart with 10 bars, data from any additional bars aren't included in the calculation.
  • You can't add a reference line to 100% stacked charts.
  • Stacked column, stacked bar, and stacked area charts only support constant value and parameter reference lines.

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