# On-line Tool for CreatingCustom, Interactive Nomograms

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Nomograms, sometimes referred to as alignment charts, are graphical calculators closely related to the old-fashioned slide rule. Before the advent of handheld calculators, nomograms were extensively used by engineers for design calculations. Despite the rapid advance of computational power, they are still of practical use in situations where it is convenient to be able to refer to typical values of the important parameters in the units most commonly employed for specific technical disciplines. This Nomogram Program is a JAVA applet which allows the user to create a customized nomogram relating three (3) parameters. An excellent SURVEY of many different types of nomograms has been compiled into a powerpoint presentation by Dr. Charles Pheatt of Emporia State University in Kansas.

The interactive graphical calculator tools created by this JAVA nomogram tool consist of three parallel scales. The leftmost and rightmost scales are designated the INPUT variables, and their values are usually known. The middle scale represents the designated TARGET variable, which is a function of the INPUT variables. It is important to point out that in fact any variable can be computed starting with the other two. The nomogram generator tool allows the user to choose among five different canonic types for the mathematical expression which the nomogram is to represent. These are: addition, subtraction, division, multiplication, and multiplication (with exponents). For each of the expressions, constant multipliers may be specified for the input variables. Among other things, these multipliers are used to account for scale factors necessitated by choice of units. In addition, minimum and maximum values for the input variables, plus names and units for all variables may be specified by the user. The user can also adjust the spacing of the tick marks on each of the scales.

To use this program, CLICK HERE, then follow the instructions to enter the required inputs for the expression in the text boxes within the pop-up windows as they appear. Once all parameters have been entered, the expression you have specified will appear at the top of the screen in the applet window and the nomogram will appear below it. The user can then use the mouse to draw a line across the nomogram by holding the button down and dragging. The program determines the values for the variables at the intersections of the scales with the line that has been drawn. Values for all variables in the output window are rounded off to three significant digits.

One example of an interactive nomogram is found in the Electrostatics Demonstration web page: CLICK HERE to learn about it.

Another on-line, interactive nomogram, presented in a slightly different form, computes the Likelihood Ratio, a statistical measure used in the biomedical field, Clink to the Minervation.com site to investigate it. This nomogram replaces the straight lines of common nomogram construction with arrows pointing to the values on each of the scales, thereby improving readability. Another site, overly chatty but still containing very useful information about nomograms is at the MathForm site.