What is “data cleansing” about? Data analysis, in practice, consists typically of some different steps which can be subsumed as “preparing data” and “model data” (not considering communication here): (Inspired by this) Often, the first major part — “prepare” — is the most time consuming. This can be lamented since many analysts prefer the cool modeling aspects (since I want to show my math!). In practice, one rather has to get his (her) hands …