Technology Tales

Creating waterfall plots in SAS using PROC GCHART

17^th March 2012

Recently, I needed to create a waterfall plot couldn't use PROC SGPLOT since it was incompatible with publishing macros that use PROC GREPLAY on the platform that I was using; SGPLOT doesn't generate plots in SAS catalogues but directly creates graphics files instead. Therefore, I decided that PROC GCHART needed to be given a go, and it delivered what was needed.

The first step is to get the data into the required sort order:

proc sort data=temp;
    by descending result;
run;

Then, it is time to add an ID variable for use in the plot's X-axis (or midpoint axis in PROC GCHART) using an implied value retention to ensure that every record in the dataset had a unique identifier:

data temp;
    set temp;
    id+1;
run;

After that, axes have to be set up as needed. For instance, the X-axis (the axis2 statement below) needs to be just a line with no labels or tick marks on there and the Y-axis was fully set up with these, turning the label from vertical to horizontal as needed with the ANGLE option controlling the overall angle of the word(s) and the ROTATE option dealing with the letters, and a range declaration using the ORDER option.

axis1 label=none major=none minor=none value=none;
axis2 label=(rotate=0 angle=90 "Result") order=(-50 to 80 by 10);

With the axis statements declared, the GCHART procedure can be defined. Of this, the VBAR statement is the engine of the plot creation, with the ID variable used for the midpoint axis and the result variable used as the summary variable for the Y-axis. The DISCRETE keyword is needed to produce a bar for every value of the ID variable, or GCHART will bundle them by default. Next, references for the above axis statements (MAXIS option for midpoint axis and AXIS option for Y-axis) are added, and the plot definition is complete. One thing that has to be remembered is that GCHART uses run group processing, so a QUIT statement is needed at the end to close it at execution time. This feature has its uses and appears in other procedures too, though SAS procedures generally are concluded by a RUN statement.

proc gchart data=temp;
    vbar id / sumvar=result discrete axis=axis2 maxis=axis1;
run;
quit;