Tetrachart is a comprehensive information graphic to understand trends throughout time. It shows trends with moving and colored bobbles, where the bubbles represent a dimension.

# 1 Description

In this type of graphics, it is possible to combine simultaneously up to four measures for one dimension. The different measures are represented by:

• The x-axis
• The y-axis
• The size (radius) of the bubbles
• The color of the bubbles

The graph changes over time by clicking on the play button.

There is no master table for entities (dimensions) in tetra charts: they are implicit in the displayed data.

## 1.1 The elements

The elements that make up a tetrachart are detailed below.

### 1.1.1 Indicators

The indicators are the measures that will be shown in the graph. The name of the measures corresponds to the indicatorname and the values are obtained from the tableprovider. It is mandatory to define whether this data will be shown in the graph, by default, according to a linear or a logarithmic scale.

The indicator category and subcategory allow classifying measures within menus and submenus and thus facilitate the selection to the user when there are many options. The system also allows indicating the data provider using the dataprovider as well as the origin through the dataprovider_link field.

By agreement, the indicator tableprovider is defined as follows:

• Rows correspond to the dimension of the graph.
• Columns correspond to the time unit of the timeline.
Any indicator can be selected to be represented on any of the axes: x-axis, y-axis, radio-axis and color-axis.

### 1.1.2 Categories

The fourth axis, which corresponds to the color of the bubbles, allows the measure to be replaced by a category. In this way, the bubbles do not change color over time, but each color represents a categorization of the analyzed dimension. For example, if the dimension were countries, the color would allow them to be classified according to their majority religion, each color representing the religion of that country.

Categories are defined by the categoryname and its values by the tableprovider.

By agreement, the category tableprovider is defined as follows:

• The entity column correspond to the dimension of the graphic.
• The group column correspond to the discrete value for the dimension.

Only the color-axis can represent the categories.

### 1.1.3 Time events

The timeline is a visualization of events over time. The time events highlight important points in the timeline with information that people might otherwise miss. Time events allow users to understand the context that these events provoke in the measures.

Time events are defined by the date field time_event and its description event_text.

# 2 Example

Tetracharts are form objects with a tetra-chart type layout.

Parameterization of the box:

• DATA
• Indicators table: defines the table for the indicators
• Categories table: defines the table for the categories
• Events table: defines the table for the time events
• INITIAL VALUES
• x-Axis: defines the indicator data for this axis
• y-Axis: defines the indicator data for this axis
• color-Axis: defines the indicator data for this axis
• radio-Axis: defines the indicator data for this axis
• SQL STATEMENT
Copy
<select>
<columns>
category,
subcategory,
indicatorname,
indicator_def,
tableprovider
</columns>
<from table='gapminder_indicators' />
</select>

# 3 Interaction

The user can interact with the graph in various ways, detailed below.

1. Axis measure selection. Select any indicator on any of the four axis.
2. Category selection. Use color to group countries by one category.
3. Relative size of bubbles. Modify the relative size of bubbles to control visual representation of very small or big values.
4. Time control. Drag the handle on the time slide bar to change the time period. Click on the play or stop button to control the animation. Show the current time event.
5. Dimension. Select or deselect one or various entities with the checkbox. The dimension bobble will stand out from the rest. Click on the bobble and see the line evolution of the dimension through time.

Watch the video demonstration.