On 2011-09-16 16:27, andrewH wrote:
Dear Bill-- Wow. This is very clever and I learned a lot from it. I've never seen the ...() trick before, and on a Google code search, I could not find anyone else who had used it. And I've never used the "..." feature, which, BTW, though mentioned in every intro to R text, has no help page I can find. <grrr>
Look for 'dot-dot-dot' in the 'R Language Definition' manual (sec. 2.1.9). Peter Ehlers
Your function is still not doing what I am trying to do, doubtless because I was not clear enough in the question I pose At the bottom of this message I have posted a copy of my testing function, and a few objects to test it on. Its details are unimportant and not very interesting, but note that all of its important outputs are in the form of side effects. What I would like to be able to do is this: f(fun,<n variable names>) and get back this: fun(variable#1) fun(variable#2) ... fun(variable#n) Attempting to copy some of your techniques, I came up with this: evaluate<- function(fun, ...){ unevaluatedArgs<- substitute(...) for (i in 1:length(deparse(unevaluatedArgs))) fun(deparse(unevaluatedArgs)[i]) invisible(TRUE) } As applied to my test data, it works on the first variable (but gets the variable name wrong) and ignores the remainder of the list, e.g.:evaluate(testX, H.char, H.vec, H.df, H.mat)################### testX( deparse(unevaluatedArgs)[i] ): Class= character Type= character Mode= character Summary: Length Class Mode 1 character character Structure: chr "H.char" On the other hand, this almost works: evaluate<- function(fun, ...){ evaluatedArgs<- list(...) for (i in 1:length(evaluatedArgs)) fun(evaluatedArgs[i]) invisible(TRUE) } The only thing it does not do is get the name of the passed object right. That seems like it ought to be a small problem, but as you pointed out, the names are not in the list. (BTW, I don't understand dropping the names as a design choice for the list() function. If you use list() to make a list out of four symbols for objects, wouldn't it be better to make the text of the symbols the default names for those objects? That would solve this problem nicely.) [s]ubstitute seems to drop all but the first variable passed by "...". Thanks so much for your thoughtful help. andrewH testX<- function(objectX, bar=TRUE) { # A useful diagnostic function object.name<- deparse(substitute(objectX)) if(bar) cat("##################################\n"); cat("testX(", object.name, "): "); cat(" Class=", class(objectX)); cat(" Type=", typeof(objectX)); cat(" Mode=", mode(objectX), "\n"); cat("Summary:\n"); print(summary(objectX)) cat("Structure:\n"); str(objectX); if (is.factor(objectX)) {cat("Levels: ", levels(objectX), "\n"); cat("Length: ", length(objectX), "\n")} invisible(object.name) } ## Define 4 test variables: H.char, H.vec, H.df, H.mat H.char<- letters[1:10] H.vec<- c(1:10) H.df<- { # Makes a test data set A.df with 2-, 3-,& 4-factor sorting variables, making 24 # combinations,& a 4th variable with a unique data value for each combination. # No random component. year.2<- factor( rep(1:2, each=12) ) cohort.3<- factor( rep(rep(1:3,each=4),2) ) race.4<- factor( rep(1:4, 6) ) D1<- as.numeric(as.character(year.2))*1.1 + as.numeric(as.character(cohort.3))*1.01+ as.numeric(as.character(race.4))*1.001 data.frame(year.2,cohort.3,race.4,D1) } H.mat<-matrix(1:16, 4, 4) ## End of test variables -- View this message in context: http://r.789695.n4.nabble.com/Returning-the-name-of-an-object-passed-directly-or-from-a-list-by-lapply-tp3816798p3819378.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.
