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SCI REVIEW OF SIGMAPLOT

SigmaPlot® - Exact Graphs for Exact Science
By John A. Wass, Ph.D.

Introduction

SigmaPlot is graphics software that allows scientists and engineers to accurately present findings using publication quality graphics. When used with its statistical counterpart, SigmaStat, a number of statistical tools are seamlessly integrated into the graphic functions so a complete report may be generated. Over the years, much-used functions have been automated and the software will rapidly generate error bars, regression lines and confidence intervals, axis-breaks, and non-linear curve fitting.

SigmaPlot is designed for the Windows platform and runs on Windows 98, NT, 2000, XP and with Microsoft Office 98, and requires a Pentium processor of at least 200 MHz clock speed. To make things easier on the beginner, a Graph Wizard is included to walk the user through simple, rapid graph creation. With a little practice, a facility is developed for the range of possible modifications. If certain graphics are used repetitively, templates may be created and used whenever needed. In addition, this version includes a powerful non-linear curve fitter, a large ( 32 million rows by 32 thousand columns) data worksheet, a mathematical transform language, and full support for OLE2 technology.

For users of previous versions, new features include full integration with SigmaStat, a new Notebook Manager, category data support, worksheet and symbol improvements, ODBC database import, improved histograms, and many more statistical options in the Regression Wizard.

Documentation

The software comes with an 852 page User's Manual that makes the learning curve almost flat. Chapters on worksheet basics and creating and modifying graphs will assist the novice with the bear elements of working with the software. Beyond that are more specialized chapters on 2D and 3D graphics, modifying details, publishing graphs, and using Transforms (the special programming language). The text is concisely written and lavishly illustrated and will be consulted often by the novice. The few editorial glitches (misspellings mostly) may be overlooked in light of the overall quality of this product. After a little practice help will come in the form of tutorials and FAQ's included in the software, as well as web based help.

Worksheet and Main Window

Figure 1 - Click to View Image

The main widow appears in Figure 1. It consists of the worksheet (the spreadsheet-like area), the graphics area, the Notebook Manager (Explorer-like function), the quick graphs icon area, and the menu and toolbars. Most are standard Windows fare and will be familiar to any Windows user. The specialized areas allow for fast navigation through the windows and selection of special functions. These functions not only assist in quickly modifying graphics but also make the worksheet area more like EXCEL (the transpose paste here is very useful).

Graphics

Graphics creation seems to become a bit easier with each version. The simple bar chart with error bars shown in Figure 2. took 10 seconds to create (including data import) after reading the simple tutorial. Adding more data to make a more complex bar chart, labeling the bars and adding ANOVA results to the worksheet area takes one or two minutes longer, depending upon how rapidly the user burns through the tutorial. Similar graphics for regression and curve fitting are quickly produced with error bars, drop lines, and cutoff lines (Figure 3.). The addition of axis-breaks is especially useful when graphing a variety of scientific data, as are the additions of clip art and equations, use of drawing tools, and ability to rapidly paste into PowerPoint slides.

For the more complex functions, 3D graphics are available and use is made of contour, mesh, and solid graphics (Figure 4.). The equation editor facilitates instant graphics for any valid function, and these expressions can either be typed in or cut and pasted from another source. Most of the actions allow for editing and the graphs can be made (almost) as complex as necessary. The temptation is to include as much information as possible, but more advanced users will usually go for a simpler graphic that the intended audience will appreciate and understand. SigmaPlot will excel there. As seen in Figure 1, graph/chart types include scatter, line, fill, contour, polar, bar, pie, and 3D. Each type has many subgroup choices, so the chance of not finding a needed template is nil for all but the most specific use.


Figure 2	Figure 3	Figure 4

Special Modules : Statistics and Pharmacology

When SigmaStat is purchased with SigmaPlot, the two programs are joined at the time of installation, and the full statistical power of the former is now available in the latter. This unfortunately, will increase the price of the package and decrease the use of SigmaStat as a standalone product. Still, the integration is seamless and greatly enhances the usefulness of the total package.

The biologist and chemist will find the further integration of a pharmacology module from previous versions to be especially useful. With the enclosed macro's they can do exploratory enzyme kinetics, shelf life determinations, simple ligand binding calculations from a variety of models, and standard curve analysis (straight line, quadratic, and s-shaped curve). The dialog boxes offer several variations and expedite curve analysis. For more complex formulations, the analyst can use built-in or user-defined transformations.

Summary

SigmaPlot 9 offers the expected improvements over earlier versions as well as a few surprises in the ease of use category. Where previously there was a struggle to quickly produce a complex graphic, the developers have addressed the learning curve and significantly decreased the slope. The main lesson learned is that when problems occur, read the manual: either paper or under the Help menu. If further support is needed, technical help is available by phone, fax, or email. The response is usually rapid and very helpful so keep this in mind when evaluating package versus price. SigmaPlot has been around for some time and it is always pleasing to see the ease-of-use issue addressed as it has been in this version.

A detailed synopsis of new and useful features is available at the website, and demo versions may be easily downloaded at the same site.