SOFTWARE FOR STATISTICAL GRAPHICS - AN OVERVIEW P.M. Caporal and G.J. Hahn, General Electric Company I. INTROOUCTION AND OVERVIEW only with software that provides high-Quality graphical output. Output devices, such as CRT dis­ Thus, we will not, for example, play terminals and special plot­ consider programs that only pro­ ters, which are now available duce plats on standard line for high-quality graphics, pro­ printers, although these may of­ vide the analyst new opportun­ ten be sufficient in the explor­ ities for presenting and explor­ atory stages of a data analy­ ing data. In addition to sum­ sis. Consideration will also be marizing data and performing limited to software for general statistical evaluations, the statistical analysis; offerings computer can be used to present that perform only a small number the results through attractive of analyses, e.g., regression a­ and meaningful graphical dis­ nalysiS, analysis of variance, plays. These displays are fur­ or face plots, will not be con­ ther enhanced by the increasing sidered. accessibility of color graph­ ics. As a result, individuals Fienberg (1979) reviews modern with limited statistical train­ graphical methods in statistics, ing can obtain simple, but in­ covering both presentation and cisive, graphical presentations analytical graphics and gives of the data, while a trained an­ numerous references. Chambers alyst can gain an improved un­ (1980) discusses the history and derstanding of complex data by trends of statistical computing using graphical tools for ex­ and Francis (1981) provides a ploratory data analysis. More­ comparative review of statisti­ over, obtaining such displays on cal computing. a computer, rather than manual­ ly, can significantly reduce the A total of 15 different offer­ elapsed time to get the desired ings are reviewed under the fol­ graphics and allows the analyst lowing headings: to operate in an iterative man­ ner. o Statistical graphics soft­ ware for desktop computers The marriage of statistical data (Section II). analysis and high-quality graph­ o Interfaces with, or exten­ ics has become possible through sions of, existing statisti­ the development of statistical cal packages (Section III). graphics software by software a Integrated statistical houses, graphics hardware sup­ graphics software for mini­ pliers, universities and oth­ computers and mainframes ers. Two previous papers (Section IV). (Caporal and Hahn [1981a and 1961b]) described software for Tables I and 2 give a comprehen­ high-quality graphical dis­ sive overview of the 15 offer­ plays. These papers dealt prin­ ings. Table 1 indicates the cipally with offerings for pres­ primary user of each, indicates entation graphics, many of which whether the offering is a prD­ have only limited capabilities gram or a library of subroutines for statisitical data analysis. and provides some brief descrip­ In this paper, we concentrate on tive comments. Table 2 shows software that permits the user the acquiSition costs (ranging to integrate the data analysis from $150 to $40,000 or more), and data display functions, the software source and the as­ i.e., offerings that have sociated host computers and non-trivial statistical, as well graphiC output devices. Since as data display, capabilities, these tables are self-explan­ for a wide variety of computers, atory, the information contained ranging from desktops to main­ in them will not be repeated. frames. We will, however, deal 199 The major purpose is to report flexible, and less sta­ an the various offerings - not tistically sophisticated to evaluate them. We have tried than most of the offer­ to be objective in our comments ings for larger comput­ and descriptions. However, some ers described in the degree of judgment invariably next two sections. How­ enters into such a rev1ew, es­ ever, the graphical fea­ pecially in deciding which pro­ tures of the offerings grams have sufficient statisti­ for desktop computers cal and graphical content and are comparable to those which are general enough to war­ that are discussed sub­ rant inclusion. We have aimed sequently in this paper. at describing all offerings that meet our criteria. Earlier ver­ 3. The available statisti­ sions of this paper were widely cal and graphical fea­ distributed. Suggestions, es­ tures vary greatly. pecially for additions, were so­ licited and acted upon. Also, The offerings with the most in Section V, we indicate some extensive graphics and sta­ offerings currently under devel­ tistical features are: opment. Despite this, it is possible that some relevant ap­ o The HP Series 70 plicable software, especially of Statistical Software a very recent nature, has escap­ o The HP Series 80 ed our attention. Due to lack Statistical Software of resources, we do not claim o The HP 9845 Statis­ hands-on experience with much of tics Library the software. However, we have o The HP Series 200 participated in demonstrations Statistics Library of most of the offerings. o The Tektronix Plot 50 Applications Li­ II. STATISTICAL GRAPHICS SOFTWARE brary FOR DESKTOP COMPUTERS o The Trend spotter '82 Graphics Manage­ A. Introduction ment Information System. Boardman (1982) in an arti­ cle on the future of statis­ These offerings are discussed tical computing on desktop further below. They represent computers describes various only three manufacturers and desktop computers and in­ only two of the 11 listed by cludes a representative list Boardman [19B2J. Offerings by of manufacturers. The use other manufacturers have been o­ of these computers for data mitted in this survey because analysis is rapidly increas­ they are of a specialized, ing. Many suppliers now of­ rather than general, nature. fer and sell statistical graphics packages. These B. HP Series 70 Statistical offerings have the following Software characteristics: The HP Series 70 Statistical 1. Their use is generally Software consists of librar­ limited only to the ies for: desktop computer model for which they were de­ o Basic one variable sta- veloped (or to systems tistics that emulate it). o Simple Linear Regression o Analysis of Variance 2. They are generally di­ a Correlation Coefficient rected mainly at data a Probability Distributions analysts with limited The statistical software statistical backgrounds, contains the capability of rather than at the creating graphical output. f (smaller) specialized I audience of statistici­ C. HP Series 80 Statistical ans. As a result, soft­ Software ; ware packages for desk­ top computers tend, in The HP Series 80 Statistical general, to be more Library contains sublibrar­ user-friendly, more ies for: II I ,~ 200 [ o General Statistics Unlike the other packages o Basic Statistics and for desktop computers de­ Data Manipulation scribed in this section, the o Regression Analysis Trend-Spotter 182 basiC system includes both the Capabilities for plotting actual hardware, i.e., a statistical results are con­ color CRT, as well as the tained within the sublibrar­ applicable software. Addi­ ies tional options, such as e­ quipment for hard copy out­ D. HP 9845 Statistics Library put, can be ordered. As suggested by its name, The HP 9845 Statistics Li­ Trend-Spotter is aimed prin­ brary contains sublibraries cipally at business people for: and administrators and is claimed to be 'a graphics o Basic Statistics and system designed by managers, Data Manipulation for use by managers. 1 For o General Statistics example, it permits esti­ o Statistical Graphics mation of trends and fore­ o Regression Analysis casts and includes adjust­ o Nonlinear Regression A­ ments for cost-of-living, nalysis anticipated inflation, and o Analysis of Variance seasonal effects. o Monte Carlo Simulation utilities III. INTERFACES WITH, DR EXTENSIONS o Principal Components and OF, EXISTING STATISTICAL PACKAGES Factor Analysis A. OVERVIEW Prompts guide the user through the programs. Most Sophisticated computer pack­ have the capability of pro­ ages for statistical analy­ ducing graphical displays of sis have become prominent the statistical results. during the last decade and are used extenSively by sta­ E. HP Series 200 Statistics tisticians and other data Library analysts. Some well-known examples are BMDP (Biomedi­ The HP Series 200 Statistics cal Computer Programs Library is similar to the HP P-Series), Minitab, SAS 9845 Statistics Library. (Statistical Analysis System), SPSS (Statistical F. Tektronix PLOT 50 Package for the Social Sci­ Applications Library ences), and p-stat. These offerings, and many others, The Tektronix PLOT 50 Appli­ are compared by Francis cations Library consists of (1981). Most were developed a statistical library as prior to the general avail­ well as other software. The ability of high-quality com­ statistical library consists puter graphics. As a re­ of sublibraries for: sult, the following exten­ sions for, or interfaces o Tests and Distributions with, high-quality graphics o Analysis of Variance have been developed: o Multiple Linear Regres­ sion a Three offerings invol- o Nonlinear Estimation ving the SAS package: Menus and prompts guide the The SAS/Graph exten­ user. The statistical sub­ sion to SAS libraries contain capabil­ An interface between ities for plotting statis­ SAS and the tical results. A separate Tell-A-Graf graphics time series analysis and program forecasting package is also Datagraf, an inter­ available. face to SAS, SAS/Graph, and the G. Trend-Spotter '82 Graphics Disspla graphics Management Information System package. 201 a The interface between vides interfaces to SAS, SPSS and the SPSS Graph­ SAS/Graph, and the Disspla ics Option, including an graphics subroutine pack­ interface option with age. The interface is a­ the Tell-A-Graf graphics chieved through a conversa­ program. tional language that prompts a The interface between the user for information and the Statll statistical does not require the user to analysis package and the learn either the SAS or the PlotII program. Disspla language. Thus, un­ o The interface between like the other packages de­ Sharp Associates APL scribed in this section, Functions for Statisti­ Datagraf appears as a new cal Analysis and their offering to the user.