https://doi.org/10.1351/goldbook.10120
Distance (\(d_{i,j}\)) between two objects (\(i\) and \(j\)) calculated as the sum of the absolute difference between \(k\) variables (\(x\)) that describe the objects. \[d_{i,j} = \sum\limits_{k\,=\,1}^{k\,=\,N} \vert x_{i,k} - x_{j,k}\vert\]