Aditya Bhagwat
2012-Jan-12 16:55 UTC
[R] using "list=" to force evaluation before execution
Dear all, I have noticed that the expression 'list =' is sometimes used to tell R to evaluate something before executing it. Two examples: rm(list=ls()) a = 3 myVarName = 'a' save(list=myVarName, file=...) I was wondering whether there is any documentation on this way of using "list". Which is a clearly different use than what ?list talks about, as the latter addresses the use of 'list' as a datastructure. Thanks for your help, Adi [[alternative HTML version deleted]]
Read the documentation for those two commands and you will see that 'list' is just a parameter to the function. It would have been called 'xyz' and worked the same. The is nothing special about 'list =' in this context; it is just naming a parameter to the function. On Thu, Jan 12, 2012 at 11:55 AM, Aditya Bhagwat <bhagwataditya at gmail.com> wrote:> Dear all, > > I have noticed that the expression 'list =' is sometimes used to tell R to > evaluate something before executing it. > > Two examples: > > rm(list=ls()) > > a = 3 > myVarName = 'a' > save(list=myVarName, file=...) > > > I was wondering whether there is any documentation on this way of using > "list". Which is a clearly different use than what ?list talks about, as > the latter addresses the use of 'list' as a datastructure. > > Thanks for your help, > > Adi > > ? ? ? ?[[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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.-- Jim Holtman Data Munger Guru What is the problem that you are trying to solve? Tell me what you want to do, not how you want to do it.
R. Michael Weylandt <michael.weylandt@gmail.com>
2012-Jan-12 17:04 UTC
[R] using "list=" to force evaluation before execution
Nope - you misunderstand entirely. Both of those functions have an argument named "list" and the code you quote is just the standard way of using a named argument. It could just as well read rm(salmon = ls()) but that would be absurd. The list argument gets its name from the fact it (usually) takes a list**, no more no less. Michael **Not strictly true here as ls() doesn't return a list, but just go with it. It's a vector of names, not a list in the data structure sense. On Jan 12, 2012, at 11:55 AM, Aditya Bhagwat <bhagwataditya at gmail.com> wrote:> Dear all, > > I have noticed that the expression 'list =' is sometimes used to tell R to > evaluate something before executing it. > > Two examples: > > rm(list=ls()) > > a = 3 > myVarName = 'a' > save(list=myVarName, file=...) > > > I was wondering whether there is any documentation on this way of using > "list". Which is a clearly different use than what ?list talks about, as > the latter addresses the use of 'list' as a datastructure. > > Thanks for your help, > > Adi > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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.