Nomogram
analog graphical calculator / From Wikipedia, the free encyclopedia
A nomogram,[1] alignment chart or abaque is a graph for calculation. It is a two-dimensional diagram which gives a computation of a mathematical function.
The field of nomography was invented in 1884 by the French engineer Philbert Maurice d’Ocagne (1862–1938).[2] It was used for many years to provide engineers with fast graphical calculations of complicated formulas. Nomograms use a parallel coordinate system invented by d'Ocagne rather than standard Cartesian coordinates.
A nomogram consists of a set of n scales, one for each variable in an equation. Knowing the values of n-1 variables, the value of the unknown variable can be found, or by fixing the values of some variables, the relationship between the unfixed ones can be studied.[3]
The result is got by laying a straightedge across the known values on the scales and reading the unknown value from where it crosses the scale for that variable. The virtual or drawn line created by the straightedge is called an index line or isopleth.