Histogram

A histogram visualizes the distribution of continuous data by grouping values into bins and displaying their frequency. This topic covers basic histogram configurations and examples.

Overview

A histogram uses vertical bars of varying heights to display data distribution based on frequency, count, or other statistics along the x-axis. Unlike a column chart, a histogram focuses on statistical analysis. Key differences:

A histogram shows data distribution. A column chart compares values across categories.
The x-axis of a histogram represents continuous numerical data (length, weight, time). The x-axis of a column chart represents categorical data (request methods).
Histogram bars have little or no gap between them because the data is continuous. Column chart bars have gaps to distinguish categories.

To add a chart to a dashboard, follow the steps in Add a chart to a dashboard.

Configuration examples

Basic histogram

Log on to the Simple Log Service console. In the Projects section, click the project you want.
In the left-side navigation pane, choose Dashboard > Dashboards. In the Dashboard list, click the dashboard you want. In the upper-right corner of the dashboard page, click Edit. In edit mode, choose Add > Add Chart.
On the right, configure settings in the Chart Type and Query and Analysis Configurations panels. On the left, set the time range, select a Logstore, enter your query, and then click Apply to view the chart.

In the Query and Analysis Configurations section on the right, set Axis X Field to t and Axis Y Field to c.

If the x-axis represents time, enable Time Series Mode. In this mode, Simple Log Service automatically formats the time values and displays the data distribution over time. The following query statement calculates the number of records in 30-minute intervals:
```
* | select __time__ - __time__ % 1800 as t, COUNT(*) as c group by t order by t asc limit 10000
```

Multi-dimension stacking

Log on to the Simple Log Service console. In the Projects section, click the project you want.
In the left-side navigation pane, choose Dashboard > Dashboards. In the Dashboard list, click the dashboard you want. In the upper-right corner of the dashboard page, click Edit. In edit mode, choose Add > Add Chart.
On the right, configure settings in the Histogram Settings and Query and Analysis Configurations panels. On the left, set the time range, select a Logstore, enter your query, and then click Apply to view the chart.

Enable Time Series Mode and select charts-demo as the Logstore. In the Histogram Settings section, set Direction to Vertical, Time Scale to Relative time, Time Selection to 1 Minute, Merge Columns to Stacked, and Transparency to 85. In the Query and Analysis Configurations section, set Axis X Field to t, and select GET and POST for Axis Y Field.

The following query statement calculates the number of GET and POST requests per minute:
```
* | select __time__ - __time__ % 60 as t, count_if(request_method = 'GET') as GET, count_if(request_method = 'POST') as POST group by t order by t asc limit 1000
```

General configurations

These settings apply to the entire histogram.

Basic configurations

Parameter	Description
Title	Set the title of the chart.
Display Title	When you turn on the Display Title switch, the title is displayed in the chart.
Display Border	When you turn on Display Border, a border is displayed in the chart.
Display Background	After you turn on the Display Background switch, a background color is displayed in the chart.
Display Time	After you turn on the Display Time switch, the query time is displayed in the chart.
Fixed Time	After you turn on the Fixed Time switch, the time range for the query and analysis is fixed and is not affected by the global time of the dashboard.

Standard configurations

Parameter	Description
Format	Set the display format for numbers.
Unit	Set the unit for numbers.
Number of Digits after Decimal Point	Set the number of decimal places for numbers.
Display Name	Set the display name for the field. This name overrides all other field names in the chart. To rename a specific field, use a field configuration.
Color Scheme	Select the color scheme for the chart. Built-in: Use the built-in colors. Solid: Select a single color. Threshold: Colors the chart based on configured thresholds.

Histogram settings

Parameter	Description
Direction	The orientation of the histogram. Valid values: Vertical and Horizontal.
Coordinate Scale	The x-axis interval. Applies only in non-Time Series Mode.
Time Scale	The time scale. Applies only in Time Series Mode.
Select Time Range	The time interval. Applies only in Time Series Mode.
Buckets	The number of buckets. In non-Time Series Mode, if you set the Coordinate Scale, the number of buckets is not required.
Rotation angle	The rotation angle of the text on the x-axis. This parameter is required when Direction is set to Vertical.
Merge Columns	With multiple Y-axis fields, use the Merge Columns setting to configure how bars are stacked. No: Each bar starts from the bottom of the chart. Yes: Bars are merged into one. Stacked: Bars are stacked without overlapping.
Line Width	The width of the bar borders.
Transparency	The transparency of the histogram.
Gradient Mode	The gradient mode of the histogram. Transparency: Applies a gradient based on the bar color and Transparency setting. No Gradient: Fills bars with a solid color.

Query and analysis configurations

Parameter

Description

Axis X Field

The field for the x-axis.

Default: automatically selected by SLS.

Axis Y Field

The field for the y-axis. Specify multiple fields to generate a grouped histogram.

Default: automatically selected by SLS.

Legend configurations

Parameter	Description
Display Legend	Turn on the Display Legend switch to display the legend.
Sorting Method	The sorting order of the legend items.
Legend Position	The position of the legend.
Actions	The behavior when you click a legend item. Single: Clicking a legend item shows only that item's data. Switch: Clicking a legend item toggles its visibility.
Maximum width (height)%	The maximum width and height of the legend.

Tooltip configurations

Parameter

Description

Sorting Method

The sorting order of tooltip data.

Applies when you hover over a bar.

Display Mode

The display mode of tooltip data.

Applies when you hover over a bar.

Axis x

Parameter	Description
Display Axis X	Turn on the Display Axis X switch to display the x-axis.
Axis X Title	The title of the x-axis.
Format	The time format for the x-axis. Applies only in Time Series Mode.
Axis X Height	The height of the x-axis. Default: automatically set by SLS.
Drag and Zoom	In Time Series Mode, after you drag to zoom in, you can refresh the global time or the time for the current chart.

Axis y

Parameter	Description
Display Axis Y	Turn on the Display Axis Y switch to display the y-axis.
Axis Y Title	The title of the y-axis.
Axis Y Position	The position of the y-axis.
Axis Y Width	The width of the y-axis. Default: automatically set by SLS.
Maximum Value	The maximum value of the y-axis. Default: automatically set by SLS.
Minimum Value	The minimum value of the y-axis. Default: automatically set by SLS.
Elastic Maximum Value	The elastic maximum value of the y-axis. Takes effect only when all y-axis values are less than this value. Default: automatically set by SLS.
Elastic Minimum Value	The elastic minimum value of the y-axis. Takes effect only when all y-axis values are greater than this value. Default: automatically set by SLS.
Axis Y ID	The Y-axis ID. The value can be any string. In General Configurations, this field typically has no effect. To define multiple Y-axes, configure them in Field Configuration. Y-axes with different IDs display as separate axes. The Y-axis ID takes precedence over the unit configuration in Standard Configurations. Two Y-axes with the same unit are merged into one. Two Y-axes with the same unit but different IDs display separately.

Variable substitution

Parameter

Description

Variable substitution

Variable substitution is equivalent to adding a filter of the variable type to a single chart. After you configure variable substitution in General configurations, Simple Log Service adds a filter to the upper-left corner of the current chart. You can select a value from the filter. Simple Log Service automatically replaces the variable in the query and analysis statement with the selected variable value and runs a query and analysis operation. For a configuration example, see Example 2: Set variable substitution.

Documentation

Parameter	Description
Add Documentation Link	Adds a documentation link to the upper-right corner of the chart.

Field configuration

Field configurations apply custom visualization settings to a specific query result or data column. For parameter descriptions, see General configurations.

For example, you can customize the bar color for a specific y-axis field. A > GET indicates that you are configuring the GET field from query A. A > POST indicates that you are configuring the POST field from query A.

Interactions

Configure interaction occurrences for a query result or data column to enable drill-down analysis. Supported interactions include Open Logstore, Open Saved Search, Open Dashboard, Open Trace Analysis, Open Trace Details, and Create Custom HTTP URL. Add interaction occurrences to a dashboard for drill-down analysis.

For example, A > GET configures an interaction for the GET field from query A. If the interaction for the GET field is set to Open Logstore, clicking a GET value in the histogram and then clicking Open Logstore navigates to the specified Logstore.