1 ) A method comprising: a) receiving, into a provided memory readable and writable by a provided CPU, one or more sets of digital data which can be presented in two-dimensions, each set comprising i) data values organized in sequential addresses or at set intervals of addresses, ii) the number of data values per data point, iii) a specified starting address, iv) a specified number of data points, called the length, in each presentation dimension; b) the computation of a numerical similarity signature, referred to as the equivalence signature as the volume of the presentation space, and c) the computation of a similarity distance between any two sets of digital data as the absolute value of the difference of their equivalence signatures.