On 07-Jul-2012 08:52:35 Martin Ivanov wrote: > Dear R users, > > I need a function that gets a number and returns its number of > actual decimal places. > For example f(3.14) should return 2, f(3.142) should return 3, > f(3.1400) should also return 2 and so on. Is such function already > available in R? If not, could you give me a hint how to achieve that? > > Many thanks in advance.
I'm not aware of such a function in R. In any case, it will be a tricky question to solve in full generality, since R stores numbers internally in a binary representation and the exact conversion of this representation to a decimal number may not match the exact value of the decimal representation of the original number. In particular, a number entered as a decimal representation from the keyboard, or read as such from a text file, may not be exactly matched by the internal representation in R. However, that said, the following function definition seems to do what you are asking for, for cases such as you list: f<-function(x) {min(which( x*10^(0:20)==floor(x*10^(0:20)) )) - 1} f(3.14) # [1] 2 f(3.142) # [1] 3 f(3.1400) # [1] 2 Note, however: f(123456.123456789) # [1] 9 f(123456789.123456789) #[1] 7 (a consequence of the fact that R does not have enough binary digits in its binary representation to accommodate the precision in all the decimal digits of 123456789.123456789 -- not that it can do that exactly anyway in binary, no matter how many binary digits it had available). Similarly: f(pi) # [1] 15 f(sqrt(2)) # [1] 16 which is a consequence of the fact that 2 < pi < 4, while 1 < sqrt(2) < 2, so the binary representation of pi needs 1 more binary digit for its integer part than sqrt(2) does, which it therefore has to "steal" from the fractional part. Hoping this helps, Ted. ------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@wlandres.net> Date: 07-Jul-2012 Time: 11:04:26 This message was sent by XFMail ______________________________________________ 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.