James Taylor Department of Zoology University of New Hampshire Durham, NH SIGMA-PLOT

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1 technological tools PC SAS VERSION 6.02 SAS Institute Inc., Box 8000, SAS Circle, Cary, North Carolina (919) Price variable depending on: (1) number of work stations licensed and (2) nature of licensing organization. Educational organizations receive a significant discount. PC SAS is not purchased outright but is licensed on an annual basis, incurring a renewal fee each year the license is updated. Example of cost for noneducational organization desiring up to 200 workstations: initial cost for BASE and STAT products would be $5000 and $4000 respectively, with an annual renewal fee of $3400 and $2600. PC SAS version 6.02 is officially supported only on PC DOS, although it has been installed successfully on many MS DOS machines. The only significant problems encountered in loading PC SAS on a MS DOS machine has been incompatible RESTORE commands, particularly in versions older than 3.0. SAS Institute does plan to support MS DOS in the future. PC SAS is an extensive statistical package oriented towards the biological sciences. SAS has been available on IBM mainframes for many years, and experienced SAS mainframe users will find many similarities in the PC version of SAS. It currently comprises two products, BASE and STAT, with plans for the release of several new products (particularly GRAPH) in the near future. The BASE products contains a "typical" full-screen editor for data and program entry and manipulation. BASE also contains a variety of programming statements to transform and modify data values, to produce tailored reports, and to perform simple descriptive statistical procedures such as means, frequencies, scatter plots, histograms, and correlations. Most of the features of the mainframe SAS DATA step such as functions, formats, informats, retain features, etc., are also available in PC SAS. The STAT product contains a wide range of inferential statistical procedures in the following general categories: regression, analysis of variance, categorical data analysis, multivariate analysis, discriminant analysis, and scor- ing procedures. The PC version of SAS has most of the statistical procedures available in mainframe SAS, but several of the PROC's have been combined. For example, the PC SAS procedure REG combines and replaces the mainframe SAS procedures REG, RSQUARE, and STEPWISE. PC SAS BASE is shipped on '2 floppy diskettes; STAT comes on 6 diskettes. A sample library is also included with each product. PC SAS must be installed on a fixed disk with at least 7 Mb of space for the BASE and STAT products. Our experience is that a 1 O-Mb hard disk with PC SAS leaves very little space for any other software, so we recommend a 20- Mb hard disk. PC SAS requires 450K RAM as a minimum. We highly recommend 640K, as several SAS procedures may require large amounts of memory for analysis of certain designs. Even with 640K we have run into problems of insufficient memory for analysis of experimental designs with large numbers of factors using the general linear models procedure (GLM), which is designed for unbalanced experiments. SAS Institute also suggests the installation of a math co-processor to increase speed, although the increase will probably not be substantial. The documentation for PC SAS is comprehensive and a bit awkward for the new user. There are four main manuals available: (1) SAS Introductory Guide for Personal Computers, $11.95, a helpful guide for novice SAS users only. (2) SAS Language Guide for Personal Computers, $ Necessary for all users, explains basics of PC SAS "Display Manager" which controls editor and output of programs. (3) SAS Procedures Guide for Personal Computers, $14.95, which documents BASE statistical and report-writing procedures. (4) SAS STA T Guide for Personal Computers, $14.95, which documents inferential statistical procedures available in STAT product. PC SAS contains an "on line" help facility that summarizes the manual information. There is also a menu-driven facility that new users may find helpful, but which is really little more than a fill-in-the-blanks approach with 522

2 no interactive prompting or assistance. Each organization that licenses PC SAS may designate one "consultant" for each product purchased. These consultants serve as a liaison between users and SAS Institute and are the only users allowed to contact SAS Institute concerning problems. The technical support at SAS Institute is highly accessible but "bugs" are very slow to be fixed. With a large group of users, the designated consultants can easily be overwhelmed with user problems and the amount of time necessary to install and maintain such an extensive system. Some special features of PC SAS include its ability to link to certain mainframes to run programs and to upload and download programs and data. PC SAS can also easily convert Lotus and dbase files to SAS data sets. SAS Institute plans to release several new products in the near future including color graphics, econometric analyses, and spreadsheets for financial forecasting and planning. PC SAS uses a window system called "Display Manager" to control editing, executing, and output of results. The Display Manager can be easily tailored by the user and makes very effective use of colors on a color monitor. However, PC SAS also executes well on a monochrome monitor. PC SAS is very similar to the mainframe version of SAS, and experienced SAS users will have no trouble converting to the PC. However, SAS is such an extensive system that the novice user may require a considerable investment of time and effort before feeling comfortable with the system. Once mastered, however, PC SAS represents a solution to many statistical problems. Reviewed by Ann Johnson and Larry W. Douglass Department of Animal Sciences ENVIRONMENTAL BIOLOGY COMPUTER TUTORIAL FOR MS-DOS MICROCOMPUTERS Dose-Response is an interactive tutorial program for computer-aided instruction in introductory environmental biology courses. The program illustrates the mechanics of doseresponse analyses of environmental hazards, but its primary purpose is to demonstrate aspects of scientific method: pattern recognition and search for trends; the need for clearly defined concepts; the competition between alternative hypotheses, each based on different assumptions; problems with extrapolation; and the susceptibility of conclusions to change when new observations are made. Students are prompted for an appropriate response at each step, so the program can be used with little prior computer experience. If a printer with graphics capability, and a graphics screen dump program (usually provided with the operating system), are available, hardcopy of various graphs can be made. At least 192K of memory is needed for best operation. The program cannot be used for statistical analysis. The program may be obtained from the author by (a) promising to suggest improvements, and (b) either sending a check to cover cost of disk, mailer, and postage ($5 total) or sending a formatted, double-sided floppy disk and return postage to: SIGMA-PLOT James Taylor University of New Hampshire Durham, NH Sigma-Plot 3.0. Jandel Scientific Bridgeway, Sausalito CA ( ). List price $350 (but you may be able to get a discount from your local dealer). Available for IBM computers or compatibles. Sigma-Plot is a graphics package designed primarily for use by SCientists, in contrast to many other graphics packages that are targeted at the business market. Thus it is not surprising to find that its capabilities include features such as error bars, log scales, suband superscripts in labels, cubic spline interpolation, and Greek letters, in addition to more standard features such as curve fitting (up to 10th-order polynomial), data transformation, different line types and symbols on a single graph, etc. The program requires 512K of RAM and two floppy disk drives (although 640K and a hard drive are much preferable), and can work with a variety of graphics adapters. Output is to a variety of dot matrix or laser printers, or Hewlett-Packard (or compatible) plotters. 523

3 Installation is menu driven, straightforward, and simple. The manual is well written, and organized into tutorial and reference sections. The tutorial takes the user through 10 examples of increasing complexity, each demonstrating additional features of the program. After 2-4 hours with the program we felt comfortable with it, and were able to produce attractive, useful graphs. Technical support was excellent; the few questions we had were answered quickly and accurately, and there was usually little delay in reaching an operator or knowledgeable support personnel at a tollfree number. The program is menu driven, and can be used from the keyboard or with a mouse (or other pointing device such as Jandel's digitizing tablet). The eight menus are easy to use, and help screens are available at the push of a function key. Once data are entered (the data-editing capabilities are similar to, but somewhat slower than, those of many spreadsheet programs, but DIF or ASCII files can be imported), variables are selected to construct a graph. A variety of graph types are available, including vertical and horizontal bar graphs or histograms, scatterplots (with or without lines connecting points), line charts (with or without symbols), etc. Different graph types can also be combined in one figure. Error bars can be computed from the data set you have entered, or entered directly. Labels can be placed anywhere on the graph, and edited or moved easily; they can also be enlarged or shrunk. Any combination of X and Y axes can be used to create "boxed" or free-floating graphs. Tick marks can be manipulated in a variety of ways (inside, outside, or both). Ten symbol types, 7 line types, 8 bar types and 16 colors can be used to distinguish variables. Axis scaling can be done automatically or manually. Templates can be used to speed construction of similar graphs. Text figures can be created by writing labels without axes, although this process is a bit awkward for large amounts of text. One nice feature is the ability to place up to 10 graphs on a page. Graphs can be moved about on a page easily, and the length of X and Y axes can be changed independently. Graphs can be easily and accurately superimposed to produce complex graphs with multiple variables plotted on distinct Y axes. Plot quality on an HP plotter is excellent, and the plots are produced very quickly. Some dot matrix printers, although significantly slower, produce plots that are of sufficiently high quality for submission for publication. The HP Laser Jet printer produced high-quality plots, but is very slow, and has severe limitations on graph size and the number of graphs per page that can be printed without adding additional memory to the printer. The program, good as it is, is not without shortcomings. Although four fonts are available, in a wide range of sizes, italics are not, and different fonts cannot be used for different parts of a graph (although different colors can be used for each label, tick marks, data points, etc.). The program does not do three-dimensional graphics, and stacked bar graphs have to be conjured up via overlaying graphs (this technique also allows the use of multiple fonts). When it is necessary to choose colors for a label, line, or data set, they are specified by number, but there is no quick and easy way to see them (such as a palette on the screen). An output device (printer or plotter) is chosen when the program is installed, and you must reconfigure the program to change output devices. While this step only takes a few minutes, it would be more convenient to be able to choose devices from a menu. New versions of the program are in the works, and will address some of these shortcomings, and add other capabilities suggested by current users. In short, Sigma-Plot is an excellent graphics package for use on MS-DOS computers. In case of use and flexibility it surpasses most other MS-DOS graphics software, and it comes close to some very good packages that run on the Apple Macintosh. Reviewed by David Inouye and Richard Inouye Department of Biology Idaho State University Pocatello, ID (Note: Order of authorship was determined by order of birthright and degree date, and does not necessarily represent the relative contributions to the review.) 524

4 PLOTIT 'Plot/T, version 1.3. Gracon Services, Inc Okemos Rd., Okemos, M (517) $440 for educational institutions. PlotlT advertises both statistical analysis and graphics capabilities. The program is available for DEC mainframes, Sun workstations, and PCs. The PC version requires an IBM (or compatible) computer with 640K of RAM, DOS 3.1 or higher, and a hard disk with about 1.5Mb of room; it runs faster with a math co-processor. The program comes on five floppy disks, accompanied by a PC user's guide to facilitate installation, an introductory guide, and a comprehensive user's guide (totalling a couple of kilograms). I found that PlotlT required a substantial investment of time in order to learn to make use of its many capabilities. There is, however, a "Quik" command that permits data entry and labeling of axes to produce quickly an auto-scaled bivariate plot. There is also an initial three-page menu that summarizes the major modules, and a comprehensive on-line help facility. At other points in the program one can toggle back and forth between menus and the command language. The program works most efficiently if you know the commands and can enter them without having to look them up, although the reference manuals were relatively easy to work with and well written. Data can be entered from the keyboard, a disk file, or a magnetic (graphics) tablet. Data files for PlotlT are stored in a special format, in a "Standard Data File." The program can use (through a utility program) ASCII files output from other commonly used programs, such as spreadsheets, if data variables are separated by commas or blanks; it can also read fixed-field FORTRAN specifications. The data editor has all the requisite capabilities, and is not hard to use. The data module also has the capability of transforming data sets, with a menu of 24 standard transformations, which can be combined to perform complex tranformations. When the data are being saved the program automatically puts a series of summary statistics on the screen, which help in scaling axes or keeping track of missing values. Data can also be sorted in a variety of ways. Statistical analyses available as part of the program include regression (simple and polynomial), time series and trend analysis, goodness of fit testing, fitting of stochastic distributions, and a series of statistics for independence of data. The output of the statistics routines is satisfactory, but this is not the package to rely on for heavy-duty statistical work. The program does not support the use of math co-processor chips. The primary strength of the program is its graphics capabilities. In terms of its capabilities and examples, the program appears to fall in about the middle of the spectrum from business to scientific graphics packages. It does, for example, have the capability of handling error bars, but also can produce charts, tables or signs in a variety of fonts (which may make for attractive poster presentations). Once data are stored in a data file they can be used (if appropriate) with the 35 different types of curves built into the program (e.g., point, step, trace, histogram, bar, contour, notchbox, etc.). User-supplied FORTRAN functions can also be fitted and plotted (although users need not write and compile their own FORTRAN statements unless they want to, since the program interprets and evaluates valid FORTRAN statements). Pie diagrams are also easily produced, as are three-dimensional surface plots (including stereoscopic pairs). The details for graph construction are stored in "parameter files," which can be edited to refine or change graphs; thus a combination of a data file and a parameter file is required to produce each graph. The flexibility of the program is apparent when a parameter file is displayed. For example, up to 25 aspects of each axis can be specified, including its origin, length, scaling, tick increments and size, color, and titles. The size, font, color and positioning of labels are easily manipulated, and on bar graphs, the bar width, fill type, and shading angle can be controlled. Symbol style and size are also controlled by the user. Once generated, graphs can be printed or plotted; the program supports a large number of printers (including laser printers) and plotters. In summary, the program is quite powerful, but perhaps not as easy to use as some other graphics packages. The statistical capabilities are useful, but not the reason to buy the program; PlotlT's forte is the integration of graphics and their underlying statistics. As seems to be the case with most graphics 525

5 packages, a new version is in the works, and prospective users may want to contact Gracon Services to get details. Reviewed by David W. Inouye 526