On 09-Nov-10 13:21:10, Shant Ch wrote: > Hi, > I want to use a more accurate value of exp(1)._ The value given > by R is 2.718282. I want a value which has more than 15 decimal > places. Can anyone let me know how can I increase the accuracy level. > > Actually there are some large multipliers of exp(1) in my whole > expression, and I want a more accurate result at the last step > of my program, and for that I need to use highly accurate value > of exp(1). > > Can anyone help me out? Thanks. > Shant
Where the value of exp(1) as computed by R is concerned, you have been deceived by what R displays ("prints") on screen. The default is to display any number to 7 digits of accuracy, but that is not the accuracy of the number held internally by R: exp(1) # [1] 2.718282 exp(1) - 2.718282 # [1] -1.715410e-07 You can get a particular result to be displayed to greater accuracy by using print(..., digits=...) (and the "digits" argument is the one in second position, so you don;t necessarily need to use "digits=". Therefore: print(exp(1),17) # [1] 2.718281828459045 (and you will not get greater precision by using more digits, e.g. 18,19,...). print(exp(1)-2.718281828459045,19) [1] 0 So 2.718281828459045 is the greatest accuracy you can get with normal 32-bit R. This is the value which will be computed by R for any instance of exp(1), and which will be stored as the value of Y in: Y <- exp(1) If you want to see all computed results displayed to more than 7 digits of accuracy, you can set the global "digits" option: options(digits=17) exp(1) # [1] 2.718281828459045 pi # [1] 3.141592653589793 See the entry for "digits" in ?options. Hoping this helps, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@wlandres.net> Fax-to-email: +44 (0)870 094 0861 Date: 09-Nov-10 Time: 13:42:17 ------------------------------ 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.