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Histogram

Histograms calculate the distribution of values and present them as a bar chart. Each bar represents a bucket; the y-axis and the height of each bar represent the count of values that fall into each bucket, and the x-axis represents the value range.

For example, if you want to understand the distribution of people’s heights, you can use a histogram visualization to identify patterns or insights in the data distribution:

You can use a histogram visualization if you need to:

• Visualize and analyze data distributions over a specific time range to see how frequently certain values occur.
• Identify any outliers in your data distribution.
• Provide statistical analysis to help with decision-making

Configure a histogram visualization

Once you’ve created a dashboard, the following video shows you how to configure a histogram visualization:

Supported data formats

Histograms support time series and any table results with one or more numerical fields.

Examples

The following tables are examples of the type of data you need for a histogram visualization and how it should be formatted.

Time-series table

The data is converted as follows:

Basic numerical table

The data is converted as follows:

Panel options

In the Panel options section of the panel editor pane, you set basic options like the panel title and description. You can also configure repeating panels in this section. To learn more, refer to Configure panel options.

Histogram options

Use the following options to refine your histogram visualization.

Bucket size

The size of the buckets. Leave this empty for automatic bucket sizing (~10% of the full range).

Bucket offset

If the first bucket should not start at zero. A non-zero offset has the effect of shifting the aggregation window. For example, 5-sized buckets that are 0-5, 5-10, 10-15 with a default 0 offset would become 2-7, 7-12, 12-17 with an offset of 2; offsets of 0, 5, or 10, in this case, would effectively do nothing. Typically, this option would be used with an explicitly defined bucket size rather than automatic. For this setting to affect, the offset amount should be greater than 0 and less than the bucket size; values outside this range will have the same effect as values within this range.

Combine series

This will merge all series and fields into a combined histogram.

Line width

Controls line width of the bars.

Fill opacity

Controls the fill opacity bars.

Gradient mode

Set the mode of the gradient fill. Fill gradient is based on the line color. To change the color, use the standard color scheme field option.

Gradient display is influenced by the Fill opacity setting.

None

No gradient fill. This is the default setting.

Opacity

Transparency of the gradient is calculated based on the values on the Y-axis. The opacity of the fill is increasing with the values on the Y-axis.

Hue

Gradient color is generated based on the hue of the line color.

Standard options

Standard options in the panel editor pane let you change how field data is displayed in your visualizations. When you set a standard option, the change is applied to all fields or series. For more granular control over the display of fields, refer to Configure overrides.

You can customize the following standard options:

• Unit - Choose which unit a field should use.
• Min/Max - Set the minimum and maximum values used in percentage threshold calculations or leave these field empty for them to be calculated automatically.
• Field min/max - Enable Field min/max to have Grafana calculate the min or max of each field individually, based on the minimum or maximum value of the field.
• Decimals - Specify the number of decimals Grafana includes in the rendered value.
• Display name - Set the display title of all fields. You can use variables in the field title.
• Color scheme - Set single or multiple colors for your entire visualization.
• No value - Enter what Grafana should display if the field value is empty or null. The default value is a hyphen (-).

To learn more, refer to Configure standard options.

Legend options

Legend options control the series names and statistics that appear under or to the right of the graph. For more information about the legend, refer to Configure a legend.

Visibility

Toggle the switch to turn the legend on or off.

Mode

Use these settings to define how the legend appears in your visualization.

• List - Displays the legend as a list. This is a default display mode of the legend.
• Table - Displays the legend as a table.

Placement

Choose where to display the legend.

• Bottom - Below the graph.
• Right - To the right of the graph.

Width

Control how wide the legend is when placed on the right side of the visualization. This option is only displayed if you set the legend placement to Right.

Values

Choose which of the standard calculations to show in the legend. You can have more than one.

Value mappings

Value mapping is a technique you can use to change how data appears in a visualization.

For each value mapping, set the following options:

• Condition - Choose what’s mapped to the display text and (optionally) color:
  • Value - Specific values
  • Range - Numerical ranges
  • Regex - Regular expressions
  • Special - Special values like Null, NaN (not a number), or boolean values like true and false
• Display text
• Color (Optional)
• Icon (Canvas only)

To learn more, refer to Configure value mappings.

Thresholds

A threshold is a value or limit you set for a metric that’s reflected visually when it’s met or exceeded. Thresholds are one way you can conditionally style and color your visualizations based on query results.

Set the following options:

• Value - Set the value for each threshold.
• Thresholds mode - Choose from:
  • Absolute
  • Percentage

To learn more, refer to Configure thresholds.

Data links

Data links allow you to link to other panels, dashboards, and external resources while maintaining the context of the source panel. You can create links that include the series name or even the value under the cursor.

For each data link, set the following options:

• Title
• URL
• Open in new tab

To learn more, refer to Configure data links.

Field overrides

Overrides allow you to customize visualization settings for specific fields or series. When you add an override rule, it targets a particular set of fields and lets you define multiple options for how that field is displayed.

Choose from one the following override options:

• Fields with name - Select a field from the list of all available fields.
• Fields with name matching regex - Specify fields to override with a regular expression.
• Fields with type - Select fields by type, such as string, numeric, or time.
• Fields returned by query - Select all fields returned by a specific query, such as A, B, or C.
• Fields with values - Select all fields returned by your defined reducer condition, such as Min, Max, Count, Total.

To learn more, refer to Configure field overrides.