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Scatter Charts

A Scatter (Point) chart shows correlations between two sets of values, enables users to observe the dependence of one value to another, and is often used for scientific data modeling.

Scatter charts are typically not used with time-dependent data where a Line chart is more suited. A common usage of the Scatter chart is to compare aggregated data across categories.

Scatter charts are different from other chart types because, instead of using the category values as X-values, they have explicit X-values for the data points. Consequently, the data can be grouped and aggregated into a different category than the value that is shown on the X-axis. For example, to show last year's sales for individual salespersons along the X-axis, you will not aggregate Y-values if two salespersons have identical X-values.

The following image illustrates a Scatter chart:

A basic Scatter chart type

Types

Bubble charts are a variation of the Scatter charts in which the data points are replaced with bubbles. This chart type displays the differences between data points based on the size of the bubble. The larger the bubble is, the larger the difference between the two data points is.

The following Bubble chart sample report has a category set to a sales person so that it aggregates sales data per sales person. However, the value of last year's sales is shown on the X-axis.

A basic Bubble chart type

Creating Scatter Charts

In this section, you will create a Bubble chart.

1. Add the Graph

To add a new Graph report item to the report, refer to the article getting started with the Graph report item.

2. Set the SeriesGroups Hierarchy

Now you can set the SeriesGropus hierarchy of the Bubble chart:

  1. Open the SeriesGroups collection editor and click Add.
  2. Set the Groupings to =Fields.Name.
  3. Set the Sortings to =Sum(Fields.SubTotal) with Desc order.
  4. Set the Name to seriesGroup1.

3. Set the CategoryGroups Hierarchy

Next, you will have to define the CategoryGroups hierarchy of the Bubble chart:

  1. Open the CategoryGroups collection editor and click Add. By default, this will add a new static group (group without grouping).
  2. Set the Name to categoryGroup1.

4. Configure the Coordinate System

Here you will specify the coordinate system details:

  1. Open the CoordinateSystems collection editor and Add a new CartesianCoordinateSystem.
  2. Leave the Name to cartesianCoordinateSystem1.
  3. Set the XAxis to New Axis with Numerical Scale.
  4. Set the YAxis to New Axis with Numerical Scale.

5. Configure the Series

In this step, you will configure the series of the chart:

  1. Open the Series collection editor and Add new LineSeries.
  2. Set the CategoryGroup to categoryGroup1.
  3. Set the SeriesGroup to seriesGroup1.
  4. Set the CoordinateSystem to cartesianCoordinateSystem1.
  5. Set the X value to =Sum(IIF(Fields.OrderDate.Year=2003, Fields.SubTotal, 0)).
  6. Set the Y value to =Sum(IIF(Fields.OrderDate.Year=2004, Fields.SubTotal, 0)).
  7. Set the Size expression to =Sum(IIF(Fields.OrderDate.Year=2004, Fields.SubTotal, 0)) - Sum(IIF(Fields.OrderDate.Year=2003, Fields.SubTotal, 0)).
  8. Set the LineStyle.Visible to False.
  9. Set the DataPointStyle.Visible to True.
  10. Set the MarkerType to Circle.

6. Style the Appearance

To set the color palette, format the labels, define the values of the legend, and elaborate on any other styling options, refer to the section on formatting the Graph.

Design Considerations

  • Scatter charts usually display and compare numeric values, such as scientific, statistical, and engineering data.
  • A typical usage of the Scatter chart is when you want to compare large numbers of data points not related to time. The more data you include in a scatter chart, the better the comparisons that you can make.
  • The bubble chart requires an additional value per data point, the Size of the bubble.
  • Scatter charts are most suitable for handling the distribution of values and clusters of data points. This is the best chart type if your dataset contains many points, for example, several thousand points. Displaying multiple series on a Point chart is visually distracting, and you have to avoid it and consider using a Line chart.

See Also

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