The time variable is most commonly plotted precisely as recorded in graphs showing change over time. However, if the most interesting part of the graph is very crowded, then transforming the time axis to give that part more space is worth consideration. In this column, I discuss logarithmic...

Ronald Aylmer Fisher suggested transforming correlations by using the inverse hyperbolic tangent, or atanh function, a device often called Fisher's z transformation. This article reviews that function and its inverse, the hyperbolic tangent, or tanh function, with discussions of their...