How to create a scatter plot with marginal histograms in SAS

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Many people know that the SGPLOT procedure in SAS 9.2 can create a large number of interesting graphs. Some people also know how to create a panel of graphs (all of the same type) by using the SGPANEL procedure. But did you know that you can also create a panel of graphs of different types in SAS by writing a template that describes how to layout each plot within the panel? Even better, there is a gallery of pre-written templates so that for many situations you don't have to write (or even understand) the Graph Template Language (GTL). You can simply copy a pre-written template!

This blog post shows how to create a scatter plot with marginal histograms in SAS by copying a pre-written template. You can download the SAS program and use the template in your own work.

Galleries of Statistical Graphics

When I want to create a plot that is somewhat complicated, the first thing I do is to look in the SAS/GRAPH Graphics Gallery. In particular, I use the galleries for the ODS Statistical Graphics (SG) procedures:

The graph that I want to produce is in the PROC SGRENDER gallery (Sample 35172), which links to a SAS Knowledge Base article on how to use the Graph Template Language (GTL) to produce a distribution plot.

How to Create a Scatter Plot with Marginal Histograms

Using the SAS Knowledge Base article as a guide, the following steps create a scatter plot with marginal histograms (download the program):

  1. Click on the Full Code tab to display the SAS program that generates the graph.
  2. Copy the first call to the TEMPLATE procedure into your SAS session:
    proc template;
      define statgraph scatterhist;
      ...
    run;
  3. Modify the example code, if necessary, to fit your needs. For example, I made the following changes:
    • I don't want transparent markers for my scatter plot, so I set datatransparency=0 on the SCATTERPLOT statement. (You can use transparency to help deal with overplotting in scatter plots.) Optionally, you can use a parameter to specify at run time whether to use semi-transparent markers.
    • I don't want the text "NOBS = number of points" to appear in the upper right portion of the plot, so I replace that text with an empty string.
  4. Run the PROC TEMPLATE code to create the template.
  5. Copy the PROC SGRENDER code at the end of the program and modify it to run on your data. For example, the following statements call PROC SGRENDER to produce a scatter plot with marginal histograms on the Height and Weight variables in the SasHelp.Class data set:
    /** create panel of plots using the ScatterHist template **/
    ods graphics;
    proc sgrender data=SasHelp.Class template=scatterhist;  
      dynamic YVAR="Weight" XVAR="Height" 
              TITLE="Height-Weight Relationship";
    run;

The SGRENDER procedure uses the ScatterHist template to layout the scatter plot and histograms, as shown below:

In this example, I modified the GTL template in a minor way, but I also could have used the template as it is. You can learn more about the Graph Template Language if you decide to modify templates or to write your own templates. I also recommend the book Statistical Graphics in SAS: An Introduction to the Graph Template Language and the Statistical Graphics Procedures by my colleague, Warren Kuhfeld.

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About Author

Rick Wicklin

Distinguished Researcher in Computational Statistics

Rick Wicklin, PhD, is a distinguished researcher in computational statistics at SAS and is a principal developer of SAS/IML software. His areas of expertise include computational statistics, simulation, statistical graphics, and modern methods in statistical data analysis. Rick is author of the books Statistical Programming with SAS/IML Software and Simulating Data with SAS.

3 Comments

  1. Renee Harper on

    Rick,
    I'm so glad to see you highlight this content. It is one of our greatest untapped gems. I have an upcoming meeting to discuss updates and more content, so keep an eye on this growing resource.

    -Renee

  2. I am very new to SAS, so please pardon the simplicity of this question. Thanks to your clear instructions, I have successfully executed the code with my own data. Right now I have one scatter-histo-plot for all the data - students in 6-10th grade , but I would like to have separate plots for each grade. Is there a simple way to do this? Ideally I'd have one image with five separate plots. Thank you!

    • Rick Wicklin

      Welcome to SAS! I think you want to use the BY statement. Almost every SAS procedure has a BY statement, including SGRENDER. If you have a variable called GRADE with the values 6,7,...,10, use PROC SORT to sort the data BY GRADE. Then in the SGRENDER procedure, include the statement
      BY GRADE;

      Since you are new, let me tell you about the SAS support communities. These are places for anyone to discuss "how do I do..." in SAS. There is a community for "SAS/GRAPH and ODS Graphics" that can help you with additional questions like this. There are also other forums on the DATA step, statistical procedures, and so forth. Enjoy!

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