simple statistics operations on tree entries compute variance from sums
creates histograms normalized to one normalize histogram by its integral
parser for TString phrase with items separated by a character
parse option string for ANN methods returns the square-root of a symmetric matrix: symMat = sqrtMat*sqrtMat
turns covariance into correlation matrix
check spline quality by comparison with initial histogram
re-arrange a vector of arrays (vectors) in a way such that the first array is ordered, and the other arrays reshuffeld accordingly
check if input string contains regular expression
routines for formatted output -----------------