How to Create a Scatterplot Matrix

What is a Scatterplot Matrix

N numeric variables can be paired in a table of charts with N x N cells. This is called a Scatterplot Matrix, or Scatter Matrix, or SPLOM.

Each chart shows a scatterplot for the variables (i, j). The lower-left corner is mirrored in the charts from the upper-right corner, in the sense for each scatterplot chart with vertical axis for variable i, and horizontal axis for variable j, there is a chart with vertical axis for j, and horizontal axis for i.

The main diagonal shows info for one single variable i: either as a Histogram, a Density Plot, or just the name of the variable.

Steps to Create a Scatterplot Matrix

Start Visual Xtractor or Data Xtractor. Connect to a database. Create or design a SQL query. Run the query and check the results.

1. Display and enable the Chart query builder.
2. Select two or more numeric columns as Point Charts – Scatter Matrix.
3. Select an optional Category, for points with different colors in MultiColor mode.

Scatterplot Matrix with Three Variables

The Scatterplot Matrix below combines the charts for three numeric variables, identified by the Scatter Matrix chart selections. Axis titles are displayed only on the left and bottom edges, when we show either Histograms or Density Plots for the individual variables on the main diagonal.

A Scatterplot Matrix is indeed a particular case of split chart. It can be also synchronized, but the histograms or density plots may not display properly.

Scatterplot Matrix with Category

When you select an additional numeric column as Category, its distinct values appear as legend items instead. In a multi-color chart, the points related to each category value appear with a different color.

Without a category, you may use the legend items to hide individual charts. With a category, you hide all points, from any Scatter charts, that appear on the same rows with those category values.

Customize your Scatterplot Matrix

1. Show the Scatterplot Matrix as multi-color. With no Category, each chart uses series with different colors. With a Category, the scatter points for each category value get a different color.
2. Hide the plot axes all together, to show just rectangular plots in the Scatter charts.
3. Select between Histogram charts, Density Plots or just variable names, to be displayed on the main diagonal.
4. Hide all the charts from either the upper-right or the lower-left corner. Remark you may turn them back visible one by one from the legend items.
5. Continue by using the legend items to hide some charts, or specific points, when a Category is used.

Conclusion

• Creating a Scatterplot Matrix in Data Xtractor or Visual Xtractor is fast and intuitive: just select two or more numeric columns as Scatter Matrix charts.
• Show Histograms or Density Plots for the individual variables.
• Hide upper or lower corners.
• Add a Category, to show points with different colors in all Scatter charts.
• All builtin powerful features of these chart type are common to most other charts: filtering series through the legend items, interactivity, monochrome or grayscale colors, rich axis and data label selections etc.
• Switch to another builtin chart theme, or customize your own, for any possible color or other styles.