An Argand diagram is a graphical way of representing a function of a complex variable, often written as *z* = *x* + *iy*, in which *x, y,* and *z* are coordinates in three-dimensional space and *i* is an imaginary number. Its true discoverer is not actually known, but Swiss mathematician Jean Robert Argand (1768–1822) is given credit for the diagram. It is thought that this was also independently discovered by Danish mathematician Casper Wessel (1745–1818), and later by German mathematician and physicist Karl Friedrich Gauss (1777–1855) in 1832 (but he probably determined it much earlier); thus, its other name is the Gaussian plane.