thanks for the detailed info. and sorry for the anonymously posting(may be subscripted with another email account, i can't specify which one is, now i subscript r-help mail list with this mail account). On Nov 8, 2007 12:48 PM, <[EMAIL PROTECTED]> wrote: > The book came out in 2002 and a lot has happened with R in the time since > then. In particular it is now possible for R to have 'lazy loading' of > objects. If the person setting up the package has used this option (as they > all now should), when the package is loaded R essentially is made aware that > the data (and other) objects are there, so it is visible, but it is only read > into memory if it is used. The little tag that alerts R to the existence of > the object and triggers the automatic loading on demand is called a 'promise' > and the action itself is called a 'delayed assign'. > > Previously this all had to be done manually. data() could be used either to > discover what data objects were available in packages, or to load them in to > memory. Many old-style packages still require you to do this. There are > cases where it is justified, I suppose, but they are quite hard to think of... > > With R you have to keep abreast of developments, and it's all happening > pretty fast. > > Bill Venables. > > PS Since you are new to R, it is not considered very friendly to send > messages to the R groups anonymously. > > > Bill Venables > CSIRO Laboratories > PO Box 120, Cleveland, 4163 > AUSTRALIA > Office Phone (email preferred): +61 7 3826 7251 > Fax (if absolutely necessary): +61 7 3826 7304 > Mobile: +61 4 8819 4402 > Home Phone: +61 7 3286 7700 > mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> > http://www.cmis.csiro.au/bill.venables/ > <http://www.cmis.csiro.au/bill.venables/> > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> > ] On Behalf Of envisage > Sent: Thursday, 8 November 2007 1:27 PM > To: r-help@r-project.org > Subject: [R] a newbie question about "data" > > hi, I am reading Modern Applied Statistics with S 4th ed。 > page4 have these two lines: > > library(MASS) > > data(chem) # needed in R only > but I find withou the line " data(chem)" > I can still access chem, isn't it? > is it unnecessary or something i missed here? > thanks for the replay in advance. > > > ______________________________________________ > 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. > >
______________________________________________ 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.
