Ron, In arithmetic, '-' and '+' are binary _and_ unary operators. That is, both -1 and 1-1 are valid arithmetic expressions, the former negates its argument, and the latter subtracts the second from the first. Since much of R is designed do arithmetic, R honors the unary _and_ binary versions of '-' and '+'. The implementation of `-`() performs negation when the second argument is missing, and subtraction when both arguments are present. AFAIR, the only other unary (but never binary) operator in R is '!', or the 'NOT' operator (maybe also the one-sided formula operator '~').
In contrast, the 'times' or 'multiply' operator '*' is generally a binary operator in arithmetic. Hence, the function `*`() requires two arguments. -Matt On Sun, 2010-08-01 at 10:56 -0400, Ron Michael wrote: > Hi friends, I am aware of the function "-"() which acts as minus in ordinary > computations. For example: > > > "-"(3, 1) > [1] 2 > > However what is the meaning of > > "-"(3) > [1] -3 > > I was expecting R to generate some error as it does for "*"(3). What is the > logic for that calculation? > > Thanks, > > > [[alternative HTML version deleted]] > -- Matthew S. Shotwell Graduate Student Division of Biostatistics and Epidemiology Medical University of South Carolina ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
