Bar Chart Widget

The Bar Chart widget represents aggregate data values as rectangular bars. The varying bar lengths help users identify data patterns and trends.

Bar chart visualization excels at comparing quantities across categories or tracking changes over time units, such as weekly or monthly trends.

Figure 160, “Bar Chart” shows an example of this widget.

Bar Chart

Figure 160. Bar Chart


Input Format

You can use the Bar Chart widget to visualize results of the groupBy() and top() functions. Unlike the Pie Chart, a bar chart can be used to show multiple aggregate results. If you provide several aggregate functions to the function argument of groupBy(), the chart will display one result per function.

This example shows multiple series per category, using log entries generated from a service:

ini
2018-10-10T01:10:11.322Z host=web01 reponseTime=10.2ms
2018-10-10T01:10:12.172Z host=web01 reponseTime=2.6ms
2018-10-10T01:10:14.122Z host=web02 reponseTime=11.5ms
2018-10-10T01:10:15.312Z host=web01 reponseTime=14.7ms
2018-10-10T01:10:16.912Z host=web03 reponseTime=10.8ms

A bar chart can compare maximum and average response time for each host.

logscale
groupBy(host, function=[max(responseTime), avg(responseTime)])

This query will produce one bar chart with three categories (one per host) and two series, one per aggregate result (_max, and _avg).

Wide or Long Input Format

The Bar Chart offers the Input Data Format property, whose Auto mode looks at the query result and automatically chooses the best interpretation of the data between long or wide data format.

  • Long data format is selected if there is more than one group field (made with groupBy([a,b])). Otherwise, Wide data input format is selected.

In Long data format mode, the first grouped field contains the categories. Subsequent grouped fields are concatenated to form the series. The first non-grouped field contains the y-value. Example:

logscale
groupBy([status, internal])
Bar Chart Selecting Long Format

Figure 161. Bar Chart Selecting Long Format


The data depicted in the below table view show what fields are visualized on the chart.

Long Format Table View

Figure 162. Long Format Table View


  • Wide: All grouped fields are concatenated and form the category (x-axis). Each non grouped field becomes a series. Example:

logscale
groupBy(status, function=[avg(contentLength, as=content), avg(time, as="time")])
Bar Chart Selecting Wide Format

Figure 163. Bar Chart Selecting Wide Format


Note

A group field is the field used as the first argument to the groupBy() function.

Attention

Charts in existing dashboards (prior to the introduction of the Auto mode) with groupBy([a,b]) queries and former default mode still set to Wide will look different as they are automatically switched to Long data input format.

Data Mapping

The default behavior of Bar Chart is to map fields based on the query result. You can overwrite this behavior by manually mapping from fields in the query result to visual properties, using the Data Mapping property. For example, the default mapping assigns the first field from a groupBy() query to the category axis. When multiple fields define the category axis, the chart creates a category for each unique value combination.

The Series definition property configures the chart to create multiple series from a single data table:

  • With the default Auto mode, the chart interprets query results to select either Fields mode or Field values mode.

  • The chart activates Field values mode when the query contains multiple group fields, as in groupBy([a,b]).

  • In all other cases, the chart operates on Fields mode.

In Field values mode, the chart creates a series name for the unique value of a field column. A secondary column determines the series values. When multiple fields define the series names, the chart creates a series for each unique value combination. Example:

Bar Chart Selecting Fields Mode View

Figure 164. Field Values Mode View


In Fields mode, the chart creates a series from each field column. The field name (column header) becomes the series name, and the corresponding field values (cell values) become the series values. Example:

Bar Chart Selecting Fields Mode

Figure 165. Fields Mode View


Widget Properties

Click the Widget icon on the right-hand side of the Event List to open the side panel and configure the following properties.

General properties:

  • Title

    The title of the widget as displayed in the dashboard. As in the example Figure 160, “Bar Chart”, it could be HTTP Methods.

  • Description

    The description of the bar chart. This is free form text supporting markdown syntax. For example, This chart shows all HTTP methods, except PUT and HEAD.

    This same description will appear in the dashboard as a tool-tip by hovering over the question mark on top of the widget.

Default time properties. The default widget time only works when Shared time is toggled off by default. Save the dashboard to set the current time selection as the default.

  • Time

  • Start

  • End

Click the Styling brush icon on the right-hand side of the Event List to open the side panel and configure the following properties.

Styling properties:

  • Layout

    • Type

      • Grouped — places series next to each other on a group for each category

      • Stacked — places series on top of each other for each category

    • Orientation sets the bars orientation as:

      • Vertical

      • Horizontal

  • Data Mapping Option available from version 1.177

    • Category displays values from the mapped field (column) by creating a category for each unique value in this column. If multiple fields define the category, the chart creates a category for each unique value combination. If left empty, the chart automatically selects the category field from the query result.

    • Series definition sets how series are created from the data. Valid options include:

      • Auto analyzes the query result to determine the series definition.

      • Fields Each series is defined by a field (column) where the column header is the series name and the cell values are the series values.

      • Field values creates series names from the value of a field (column) and a secondary column defines the series values. When multiple fields define the series, the chart creates a series for each unique value combination.

    • Series The fields used to generate series. The interpretation depends on the series definition.

    • Value When Series definition is set to Field values, this field defines the series values.

    • Max series (bars) limits the number of series shown in a category. Series with the lowest cumulative sum across categories are grouped into one series called "Other".

  • Line overlay Option available from version 1.177

    Optionally adds a line overlay in the chart. Some properties in this section vary based on the Series definition selection.

    • Series allows selecting the field series to be displayed as lines. Only applies when Series definition is Fields.

    • Value is the field that defines a secondary metric used to generate lines. Only applies when Series definition is Field values.

    • Right axis adds a separate axis on the right for the line marks. When this option is cleared, the chart uses the left axis to display both bar and line values.

  • Category axis

    • Show title checkbox to show the title for the category (horizontal) axis.

    • Title gives a title to the vertical axis.

    • Text anchor controls where the labels are positioned under each bar. Valid options are:

    • Left will bring labels closer to the bars.

    • Center

    • Right

    • Angle

      Modifies the angle of the label displayed under each bar.

    • Max length

      Sets the distance between the labels and the bottom of the widget. The distance is expressed in pixels, according to Cascading Style Sheets conventions. The more you increase the padding bottom, the more the size of the graph is reduced.

  • Value axis (left)

    • Show title shows the title chosen for the value axis on the left.

    • Title gives a title to the value axis.

    • Type The scale type for the axis. Valid options are:

      • Linear — a quantitative scale that preserve proportional differences.

      • Logarithmic — a nonlinear quantitative scale particularly useful for plotting data that varies over multiple orders of magnitude.

    • Normalize checkbox — only available in stacked charts with Value axis set to Linear, allows for data normalization.

  • Value axis (right) This section only applies and is visible in the UI when Line overlay has been configured to have a right axis.

    • Show title shows the title chosen for the value axis on the right.

    • Title gives a title to the value axis.

    • Type The scale type for the axis. Valid options are:

      • Linear — a quantitative scale that preserves proportional differences.

      • Logarithmic — a nonlinear quantitative scale particularly useful for plotting data that varies over multiple orders of magnitude.

  • Legend toggle which allows showing or hiding the legend in the chart. If selected, it prompts the following properties:

    • Labels Valid options are:

      • Truncate — shortens the length of the series for a better visualization within the chart. It is used in case of long labels that would exceed the maximum space allowed in the chart. It is the default option. Hover the mouse over a label, then press and hold ALT to momentarily see the full series.

      • Show full — shows the full name of the series, that is, the entire value is displayed in the label or tool-tip. In case of very long labels, it might affect their visibility within the chart. Hover the mouse over a label, then press and hold ALT to momentarily see the truncated series.

    • Position sets the position of the legend in the chart. Valid options are:

      • Right

      • Bottom

    • Show Title checkbox

      Allows to show or hide the legend's title.

    • Title

      Text field to enter the desired title for the legend when Show Title is ticked.

  • Bars

    • Show value on bars shows the given value for each bar.

    • Category padding

      Use this setting to control the distance between categories in the chart.

    • Series padding

      Use this setting to control the distance between bars within a category.

    • Max series count

      Limits the number of series shown in a category. Series with the lowest cumulative sum across categories will be grouped into one series called "Other".

    • Input data format

      How to interpret the result query data. Valid options are:

      • Auto is selected by default and enables automatic detection of long or wide format — for details, see Wide or Long Input Format

      • Wide — data stored in wide format has a column for each series (variable) with the series name as the header and the values as rows. For example, this format is useful when data is grouped by a single field and multiple aggregate functions are used.

      • Long — data stored in long format has a single column for each named series (variable) and a single column with the values. For example, this format is useful when data is grouped by two fields.

  • Sorting

    The default sorting is by X axis labels.

    • Order by series

      Specifies the name of the field to order the series by.

    • Order orders the series names alphabetically.

      Valid options are:

      • Ascending

      • Descending

  • Series

    Change the color of the bar series and assign them the title you want to see displayed in the chart.