StatUtils.sum returns NaN for zero-length arrays ------------------------------------------------
Key: MATH-373 URL: https://issues.apache.org/jira/browse/MATH-373 Project: Commons Math Issue Type: Bug Affects Versions: 2.1 Reporter: Roman Werpachowski StatUtils.sum returns NaN for zero-length arrays, which is: 1. inconsistent with the mathematical notion of sum: in maths, sum_{i=0}^{N-1} a_i will be 0 for N=0. In particular, the identity sum_{i=0}^{k-1} a_i + sum_{i=k}^{N-1} = sum_{i=0}^{N-1} is broken for k = 0, since NaN + x = NaN, not x. 2. introduces hard to debug erros (returning a NaN is one of the worst forms of reporting an exceptional condition, as NaNs propagate silently and require manual tracing during the debugging) 3. enforces "special case" handling when the user expects that the summed array can have a zero length. The correct behaviour is, in my opinion, to return 0.0, not NaN in the above case. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.