INTRODUCTION TO SAS/GRAPH

Transcription

1 INTRODUCTION TO SAS/GRAPH John J. Cohen Advanced Data Concepts Abstract Opening the SAS/GRAPH manual for the first time can be an intimidating experience. Rudimentary charts and plots seem to require more study than a programmer can spare. This tutorial will lessen the effort required to take advantage of SASfGRAPH. The presentation begins by examining the relationship between the response data set and the more common SAS procedures used to create displays, such as GCHART, GPLOT, and GMAP. Customizing graphics using TIlLES, FOOrnOTES, and LABELS is also covered. The presentation concludes with a discussion of hardware considerations and an exploration of the ANNOTATE and GREPLAY procedures. Introduction SAS/GRAPH offers a wonderful set of tools for displaying data graphically. Instead of producing listings and summaries, we can generate "pictures" of data which may illuminate issues not otherwise apparent (For instance, see Terry Allen, Using SASIGRAPH Sofrot:are to Detect Medicaid Fraud.) And while graphics cannot completely replace reports, we all know that a picture is worth a thousand words. Exceptional graphs will take considerable experience and effort, such as those entered in the annual SUGI graphics competition. Simple graphs, however, can be produced by anyone willing to invest a little time in understanding your data and how to best present it. The presentation tools, SAS/GRAPH, are SAS procedures and programming statements remarkably similar to those which you already use. (If you are familiar with PROC CHART or PROC GPLOT, you have a head start.) We will organize the basic SAs/GRAPH procedures by data type, offering simple examples of each. Next, we will describe common customization features, although we never want to over-customize (see Edward Tufte on chart junk). Finally, areas for additional exploration will be suggested. Examples in this paper are slightly modified versions of programs in the SAS Sample library. The Response DATA SET (your Data) Our goal is to turn your data into a picture that is more useful than a report. It is not to create fine art, although some artistic sense is helpful. Rather, you want to identify the issue in your data to be illuminated and then choose the procedures accordingly. If your data has no variables (just descriptive/text information) then PROC GSUDE would be appropriate. The bulk of our work, however, consists of displaying variables, and especially how variables relate to each other. Where at least one is categoricavordinai (cannot really be added or subtracted from each, e.g., region names), we will use PROC GCHART to create horizontal (HBAR) or vertical (VBAR) for side-by-side displays of magnitude. For depicting proportions of a whole, a pie chart (PIE) makes sense. Data where the variables of interest are interval (adding and subtracting makes sense, such as sales in dollars or trends over time) can be effectively presented using PROC GPLOT. Finally, PROC GMAP is designed to display data of a geographic nature. Simple Cnstomization Our discussion of customization will be very simple, devoted mainly to two SAS statements with which most of us have programming experience, TITLE and FOOrnOTE. These merit special consideration as exploring some of their SAS/GRAPH features will both introduce options common throughout SAS/GRAPH, as well as suggest how quickly having so many choices can become confusing.. As in Base SAS, both statements define text strings to be displayed at the top (TITLE) or bottom (FOOrnOTE) of the display. SAS/GRAPH allows us to specify text justification (left, center, or right), text height (in mystery units), and font. Color is an option to be left for the presentation and access to color output devices. For instance, a center-justified title of height 5 in font swissb would be produced by the following: 140

2 TITLE1 JUSTIFY=CENTER HEIGHT=5 FONT=SWISSB "MY FIRST SAs/GRAPH TITLE"; And that's really all there is. Specifying patterns, symbols, interpolation methods, and the like are just as simple, although beyond the scope of this discussion. Start out using the defaults that come with SAS/GRAPH procedures and build your program one step-at-a-time. PROCGSLIDE If all you have are text strings, what you want to produce is a slide. This PROC GSUDE example is a complete, if simple, SAs/GRAPH program. Note that we can abbreviate keywords (justify, height, font). We have also changed the specifications in FOOTN01EI in the middle of the text string (two heights). /* define text strings *1 TITLE! JUSTIFY=CENTER HEIGHT=5 FONT=SWISSB "Annual Summary"; FOOTNOTE1 J=R H=3 F=SWlSSB "QWERTY," H=l.5 "Inc."; FOOTNOTE2 J=L H=2.5 F=SWlSSB "PROC GSLIDE EXAMPLE"; 1* display text strings *1 PROC GSLIDE; PROC GCHART - PIE Our first chart with variables will be a pie chart displaying the proportions of total sales by region for QWERTY, Inc. We will specify TITLEs and FOOTNOTEs, the data set to display (SALES), the kind of chart desired (pie), the variable (REGION-categorical level) which describes the different pie slices, the type of statistic that the slices represent (SUM), and the variable (AMOUNT-interval level) we want summed to form the pie statistic. Options, as with many SAS procedures, are listed after a "I" (slash). 1* create the data set *1 DATA SALES; INPUT REGION $ 5 MONTH $ 3 AMOUNT; CARDS; NORTH JAN SOUTH JAN EAST FEB WEST MAR (rest of data) 1* define title and footnote *1 "QWERTY, Inc - Sales by Region"; FOOTNOTEI J=LEFT H=1 F=SWlSSB "PIE CHART EXAMPLE"; 1* generate pie chart with default patterns *1 PROC GCHART DATA=SALES; PIE REGION 1 TYPE=SUM SUMV AR=AMOUNT; PROC GCHART - HBAR All following examples use a data set (SALES) consisting of the variables STATE, NAME, NUMBER, TYPE, and AMOUNT. (These are randomly-generated sales data for the six-person sales staff of QWERTY, Inc.) From this data set we want to display a horizontal bar chart (HBAR) by salesperson (NAME-categorical) summing (SUMV AR option) across AMOUNT. The appearance of the horizontal axis is set using an AXIS statement to specify its LENGTH and the placement and labeling of axis tick marks (ORDER). We will attach a format to the NAME variable (LABEL). Finally, we will request that sum of AMOUNT be printed and attach the defined axis specifications (AXIS 1) to the axis. 1* derme title and footnote *1 "NEW ENGLAND SALES BY PERSON"; FOOTNOTEl J=L H=1 F=SWISSB "HORIZONTAL BAR CHART EXAMPLE"; 1* generate hbar chart specifying axis *1 PROC GCHART DATA=SALES; AXiSI LENGTH=50 PCT ORDER= 0 TO 6000 BY 2000; LABEL NAME='OO'X; HBAR NAMEISUMVAR = AMOUNT SUM AXIS = AXISl; 141

3 PROC GCHART - VBAR Our next chart is a vertical bar chart. Our bars will again be salespersons (NAME) but this time we will sum across the NUMBER of items sold. We will subdivide the bars (using a SUBGROUP option) on the item TYPE. We will request that our chart be FRAMEd and will specify the AXIS appearance as an option. 1* define title and footnote *1 "ITEM TYPES SOLD BY PERSON"; FOOTNOTEI J=L H=l F=SWISSB "VERTICAL BAR CHART EXAMPLE"; 1* generate vbar chart with frame *1 PROC GCHART DATA=SALES VBAR NAMEISUMVAR == NUMBER SUBGROUP = TYPE FRAME AXIS = 0 TO 1500 BY 500; PROCGPLOT To display two interval-level variables (NUMBER and AMOUNT), a scatter plot makes sense. With PROC GPLOT we may also draw lines (INTERPOLATing) between the plotted points. We may use special VALUES (diamonds, triangles, etc.) for the points. As before, we may control the appearance of the axes and request a frame. We will plot the data twice, once to generate a regression line and 95% confidence intervals (I=RCCLM95) and secondly subdivided by TYPE. The latter plot, over-laid over the first, will display the actual scatter plot with the plotted VALUE for points being defined in the SYMBOL statements. 1* define tide and footnote *1 "NUMBER OF UNITS SOLD BY TYPE"; FOOTNOTE! J=L H=l F=SWISSB "PROC GPLOT EXAMPLE"; 1* define SYMBOLS for each ploued point *1 SYMBOLl I=RCCLM95 V=NONE; SYMBOL2 I=NONE V=SQUARE; SYMBOL3 I=NONE V=DIAMONDj SYMBOL4 I=NONE V=PLUS; SYMBOLS I=NONE V=TRlANGLE; I. generate plot with frame *1 PROC GPLOT DATA=SALES AXIS! LENGTH=70 PCT; AXIS2 LENGTH=4S PCT ORDER=O TO 1000 BY 250; PLOTI AMOUNT * NUMBER I FRAME VAXIS = AXIS2 HAXIS=AXInnSl; PLon AMOUNT NUMBER = TYPE I FRAME VAXIS = AXIS2 HAXIS = AXIS!; PROCGMAP The variable STATE is certainly categorical but it also has a geographical meaning which may be best displayed with PROC GMAP. We will use one of several special MAP data sets supplied by the SAS Institute to draw the state boundaries. The SALES data then is used to shade each state. We will use PROC MEANS to create a summary data set (by state) called SALESSUM. The map data set we will use is US. We will map AMOUNT using a CHORO(PLETH) projection ---the simplest-- by STATE, our ID variable. I define tide and footnote *1 "SALES FOR NEW ENGLAND REGION"; FOOTNOTEI J=L H=l F=SWISSB "PROC GMAP EXAMPLE"; 1* summarize sales data *1 PROC MEANS DATA=SALES NOPRINT SUM; BY STATE; VAR NUMBER AMOUNT; OUTPUT OUT=SALESSUM SUM=NUMBER AMOUNT; 1* generate map using US map data set*1 PROC GMAP DATA=SALESSUM MAP=US; IDSTATE; CHORO AMOUNT; Data set US is already projected. (Coordinates were transformed to accommodate the difference between the real latitude and longitude on a spherical globe and our display on a flat map.) Other map data sets ---and your response data set-- may need to be transformed similarly using PROC GPROJECT. 142

4 Hardware Considerations or How to Get Output Working with SAS/GRAPH is facilitated by a combination of a video display device and a "hard copy" output device. Thus, you can quickly see the results of incremental modifications to your program and, when ready, create a permanent version of your graph. However, there are different programs called device drivers for different printers and monitors. Default sizing, colors, and aspect (portrait vs. landscape and square vs. rectangular) will vary, and the dynamite graph on your PC monitor may look underwhelming on the laser printer. PROC GDEVICE accesses a catalog of the specifications for each device driver. PROC GTESTIT will generate a sample of an individual device driver's output. (See Mike Kalt for additional help in making sure that What You See Is What You Get-WYSIWYG.) Additional control of hard copy output can be achieved by importing your graphics output into a word processing package and then using those tools. (See Wind and Baum, p.199, for an example of importing into WordPerfect.) Experimenting -with the graphic options (GOPTIONS) in your session may also prove helpful. (Try running PROC GOPTIONS.) Finally, you may run up against hardware limitations. For instance, your pen plotter may only have 4 colors, you have a CGA monitor, your laser printer has a resolution of 150 dots per inch, or your PC has 1 MB of memory. One solution is to upgrade or replace. When budgets aren't cooperative, an alternative is to create file output in a specialized form that can be downloaded andlor uploaded andlor imported into a different software package andlor on a different computer/operating system. The WordPerfect example mentioned above is one such process. Useful output file types include CGM, graphics stream files, and metafiles. (See the SAS manual for additional details.) When memory constraints are the problem, run your programs in batch mode instead of interactively. PROC GREPLAY PROC GREPLA Y allows one to RE-disPLA Y a graph that we created previously and saved to a graphics catalog. You can change some GOPTIONS without reprogramming and re-running the graph, and you can even REPLAY to a different output device. To save the map created in the GMAP example above to CATALOG, we add the highlighted statements: PROC GMAP DATA=SALESSUM MAP=US GOUT=CATALOG; IDSTATE; CHORO AMOUNT / NAME = 'MAP'; As with any SAS catalog or data set, saving the catalog permanently will also require a LIBNAME statement and LIBREF prefix to the GOUT catalog name. To replay the map, we define a template indicating where (at which coordinates-lower Left X, Upper Left X, etc.) the map should be displayed and the catalog in which it is stored. This example defines a template with four quadrants and will be used to display the map in the top right. It will also display the VBAR, GPLOT, and HBAR graphics. PROC GREPLAY NOFS GOUT=GREPLAY; IGOUT CATALOG; TC TEMPLATE; TDEF T2X2 1/ LLX=O ULX=O URX=SO LRX=SO LLY=SO ULY=100 URY=I00 LRY=50 COLOR = wmte 2/ LLX=50 ULX=50 URX=100 LRX=100 LLY=50 ULY=100 URY=I00 LRY=50 COLOR = WmTE 31 LLX=O ULX=O URX=SO LRX=SO LLY=O ULY=SO URY=SO LRY=O COLOR=WmTE 41 LLX=50 ULX=SO URX=l00 LRX=100 LLY=O ULY=50 URY=50LRY=O COLOR = WmTE; TEMPLATE T2X2; TPLAY l:vbar 2:MAP 3:PLOT 4:HBAR; IGOUT GREPLAY; MODIFY _lasc/name='out20.1'; QUIT; GREPLA Y templates may also be specified through a Display Manager window. (See Marc Jacobs, Introduction to PROC GREPLAY or a SASIGRAPH manual.) 143

5 Annotate Annotate data sets are specialized SAS data sets used to further customize SAS/GRAPH procedure output or to create individualized output in lieu of the regular library of procedures. By adding an ANNOTATE:: option to your procedure, both your response data set and your annotate data set will be graphed more-or-less simultaneously. This can be used to highlight a particular point in a plot or add descriptive information to your chart or map. ANNOTATE data sets are created in a DATA step and use regular SAS programming statements and specialized ANNOTATE functions and macros. The data set contains the data to be printed (text, symbols, graphics), formatting information (size, font, color), and coordinates for locating where on the graph the annotate data is to be displayed. In this example, we will annotate our map using data from another SAS Institute-supplied map data set, USCENIER. We will identify the twoletter state name and place it in the center of each state on our map. The annotate data set we create (CENTER) must have the same ID variable (STATE) as our response data set. Once the annotate data set is created, we will add it to the PROC GMAP program as highlighted below: 1* create annotate data set *1 DATA CENTER; SET USCENTER; LENGTH FUNCTION STYLE $ 8; RETAIN FLAG 0; STYLE='SWISSB'; /* font *1 XSYS='2'; 1* X & Y use map coord. system *1 YSYS='2'; WHEN='A'; 1* annotate after map is drawn *1 1* FlPS to postal code *1 TEXT=FlPSTATE(STATE); FUNCTION='LABEL'; IF FLAG=} THEN DO; 1* draw line to interior *1 FUNCTION='DRA W'; FLAG=O; END; IF OCEAN='Y' THEN DO; 1* place text in ocean *1 POSITION='6'; OUTPUT; 1* move to beginning *1 FUNCTION='MOVE'; FLAG='}'; END; OUTPUT; KEEP X Y XSYS YSYS FUNCTION STYLE WHEN POSITION TEXT; 1* generate map using annotate *1 PROC GMAP DATA=SALESSUM MAP=US; ID STATE; CHORO AMOUNTI ANNOTATE=CENTER; Conclusion Using SAS/GRAPH, as we have seen, is readily accessible to anyone with at least some experience in Base SAS. If the suggested steps are followed, you will certainly be able to produce useful graphs, and with a little work and patience, you may be entering next year's SUGI graphics competition. 1) Start simply, using what you already know about SAS and the SAS/GRAPH defaults. Build on this incrementally. Do not try to use every option in the book. (See LeRoy Bessler, Chart Smart... ) 2) Use examples as your starting point. (Save your old programs, along with sample output.) Boldly steal ideas from SAS manuals, Observations, conference papers, and your colleagues. 3) Understand your data and choose procedures accordingly. You may have to manipulate your data set prior to graphing it. 4) Keep your emphasis on graphing your data and not on producing chart junk. Develop a set of graphics standards and avoid clutter. 5) Allow plenty of time for trial-and-error in producing output. Consider developing macros for "production graphics" and save extended efforts for special applications. SAS and SAS/GRAPH are registered trademarks of SAS Institute Inc, Cary, NC, USA WordPerfect is a registered trademark of WordPerfect Corp., Orem, UT. 144

6 Bibliograpby There are many excellent resources for creating graphics using SAS/GRAPH. A few are listed here. Allen, Terry, Using SASIGRAPH Software to Detect Medicaid Fraud, SAS Institute Inc., Proceedings of the Fifteenth Annual SAS Users Group International Conference, Cary, NC: SAS Institute Inc., 1990, pp Bessler, LeRoy, Chart Smart: Designing Graphs and Tablesjor Effective Communication, SAS Institute Inc., Proceedings of the Eighteenth Annual SAS" Users Group International Conference, Cary, NC: SAS Institute Inc., 1993, pp Davis, Michael, Putting Yourself on the Map with the GMAP Procedure, to be presented at NESUG 1993, Springfield, MA. Howard, Neil, An Introduction to SASIGRAPH for New or Nervous Users, NorthEast SAS Users Group Proceedings of the Third Annual Conference., Cary, NC: SAS Institute, Inc. 1990, pp Jacobs, Marc, An Introduction to PROC GREPIAY, SAS Institute Inc., Proceedings of the Eighteenth Annual SAS "Users Group International Conference, Cary, NC: SAS Institute Inc., 1993, pp Kalt, Mike, Going from Display Graphics to Hard Copy without Tears, Observations, Vol. 1, No.1, 1991, pp SAS Institute Inc., SAS/GRAPH User's Guide: Release 6.03 Edition, Cary, NC, SAS Institute Inc, 1988 Tufte, Edward R., Tbe Visual Display of Quantitative Information, Cheshire, CT, Graphics Press, Wind, Jay Jacob and Dr. Bernard R. Baum, Excellent Maps Using SASIGRAPH - The Latest Tools and Techniques. NorthEast SAS Users Group Proceedings of the Fifth Annual Conference., Cary, NC: SAS Institute, Inc. 1992, pp

7 ~nnual SUI"I'ISry r l OCI tool!a S! ~ ~ PRoe ~ GSLIDE EXAMPLE QWERTY, Inc. Sales By Region SUH of AHOUNI' by RlCION Sales For New England Region QVVERTY, Inc. PIE CHMT IXMfIU: MOO GMAPIMNOTATE EXAMPLE AHOUN' t2 00 R:XXXJ n 00

8 Item Types Sold By Person HUHaBRl~g=1~ ' Sales For New England Region... ~ liar CHARI' 1lWlPU. -..I Burns FunkHn Johnson towallki Hartin Reese NAME TYPB IZIZIBI I 0 1 ti _Nuts _Pliers IDDID Washers Number of Units Sold by ~e PRDC GMAP IJfAIIIILR AMOUNT ~ ]600 liiiilj 4200 [JJCO 4800 New England Sales By Person "H?g~i ". 5 ". 20 ] TYPB ODDBolts VER11CAL BAR CHART EXAMPLE.0 70 NUM9I!:R.. o o o 0 ~:'a"""... :... '. " D a d'" '" 0-0- Huts... Pliers 6 A tlasbers AMOUNT 1000 ". 750, AHOUNT SUN Burns 2687 Prankl in 15t5 Johnson U18 Kowalski 4970 Martin )947 Reese U ARoun SUH HORIZONTAL BAA CHART UAMPLI = I'D 'S. E!..g i :I. ~