Hi all,
In R it is possible to sum tables: > (a <- table(rep(1:3, sample(10,3)))) 1 2 3 2 5 7 > a+a 1 2 3 4 10 14 Now suppose that I have a list of tables, where each table counts the same things > k <- list(a,a,a) How can I sum all tables in k? > do.call(sum, k) [1] 42 does not work since it sums over each table. > do.call(`+`, list(a,a)) 1 2 3 4 10 14 works not with lists containing not exactly two values (since `+` takes exactly 2 values). So I think I should write something like Summary.table <- function(..., na.rm) { if (.Generic == "sum") { ... } else { # use the default method NextMethod() } } So first question: where is the `+` operation defined for tables? Is it S4? How can I see the source code of S4 functions (I'm not very comfortable with S4)? Or in general how do I find all generic functions for a specific class? I can get all S3 implementations of plot with methods(plot), I can get all S4 functions with getMethods(plot). But I've no idea of how to find all methods defined for a class? (e.g. all functions that operate on tables, say) Second question: my first dirty hack would be something like args <- list(...) table.sum <- args[[1]] for (i in 2:length(args)) table.sum <- table.sum + args[[i]] making use of the fact that `+` is defined for tables (and forgetting about cases where two tables don't feature the same names). It works, but isn't there a more elegant way to get the same? Last question: is there a way to determine the call stack, such that I can see the names of the function which are actually executed when I commit a command? I know a little about R's dispatching mechanism for S3 classes (plot(a) actually calls plot.table) but I've no clue which function is called if I type a + a (especially since `+` belongs to the generic function group Ops and I do not know at all whether its S4 or S3). I read the documentation about S3 Group Generic Functions and tried to delve into S4, but obviously I was not able to understand everything completely. So it would be great if somebody could help me out with this specific topic and point me to some resources where I can learn more. Thanks for your help in advance. BR, Thorn ______________________________________________ [hidden email] 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. |
Reduce(`+`, k)
On Mon, Aug 23, 2010 at 12:18 PM, Thaler, Thorn, LAUSANNE, Applied Mathematics <[hidden email]> wrote: > Hi all, > > In R it is possible to sum tables: > > > (a <- table(rep(1:3, sample(10,3)))) > > 1 2 3 > 2 5 7 > > > a+a > > 1 2 3 > 4 10 14 > > Now suppose that I have a list of tables, where each table counts the > same things > > > k <- list(a,a,a) > > How can I sum all tables in k? > > > do.call(sum, k) > [1] 42 > > does not work since it sums over each table. > > > do.call(`+`, list(a,a)) > > 1 2 3 > 4 10 14 > > works not with lists containing not exactly two values (since `+` takes > exactly 2 values). So I think I should write something like > > Summary.table <- function(..., na.rm) { > if (.Generic == "sum") { > ... > } else { # use the default method > NextMethod() > } > } > > So first question: where is the `+` operation defined for tables? Is it > S4? How can I see the source code of S4 functions (I'm not very > comfortable with S4)? Or in general how do I find all generic functions > for a specific class? I can get all S3 implementations of plot with > methods(plot), I can get all S4 functions with getMethods(plot). But > I've no idea of how to find all methods defined for a class? (e.g. all > functions that operate on tables, say) > > Second question: my first dirty hack would be something like > > args <- list(...) > table.sum <- args[[1]] > for (i in 2:length(args)) table.sum <- table.sum + args[[i]] > > > making use of the fact that `+` is defined for tables (and forgetting > about cases where two tables don't feature the same names). It works, > but isn't there a more elegant way to get the same? > > Last question: is there a way to determine the call stack, such that I > can see the names of the function which are actually executed when I > commit a command? I know a little about R's dispatching mechanism for S3 > classes (plot(a) actually calls plot.table) but I've no clue which > function is called if I type a + a (especially since `+` belongs to the > generic function group Ops and I do not know at all whether its S4 or > S3). I read the documentation about S3 Group Generic Functions and tried > to delve into S4, but obviously I was not able to understand everything > completely. So it would be great if somebody could help me out with this > specific topic and point me to some resources where I can learn more. > > Thanks for your help in advance. > > BR, > > Thorn > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html> > and provide commented, minimal, self-contained, reproducible code. > [[alternative HTML version deleted]] ______________________________________________ [hidden email] 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. |
sorry, cancel that. I will try again.
On Mon, Aug 23, 2010 at 12:35 PM, RICHARD M. HEIBERGER <[hidden email]>wrote: > Reduce(`+`, k) > [[alternative HTML version deleted]] ______________________________________________ [hidden email] 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. |
In reply to this post by Richard M. Heiberger
Perfectly, works as expected. Regarding the other questions, can anybody point me to the right direction?
BR Thorn From: RICHARD M. HEIBERGER [mailto:[hidden email]] Sent: lundi 23 août 2010 18:36 To: Thaler,Thorn,LAUSANNE,Applied Mathematics Cc: [hidden email] Subject: Re: [R] Sum a list of tables Reduce(`+`, k) On Mon, Aug 23, 2010 at 12:18 PM, Thaler, Thorn, LAUSANNE, Applied Mathematics <[hidden email]> wrote: Hi all, In R it is possible to sum tables: > (a <- table(rep(1:3, sample(10,3)))) 1 2 3 2 5 7 > a+a 1 2 3 4 10 14 Now suppose that I have a list of tables, where each table counts the same things > k <- list(a,a,a) How can I sum all tables in k? > do.call(sum, k) [1] 42 does not work since it sums over each table. > do.call(`+`, list(a,a)) 1 2 3 4 10 14 works not with lists containing not exactly two values (since `+` takes exactly 2 values). So I think I should write something like Summary.table <- function(..., na.rm) { if (.Generic == "sum") { ... } else { # use the default method NextMethod() } } So first question: where is the `+` operation defined for tables? Is it S4? How can I see the source code of S4 functions (I'm not very comfortable with S4)? Or in general how do I find all generic functions for a specific class? I can get all S3 implementations of plot with methods(plot), I can get all S4 functions with getMethods(plot). But I've no idea of how to find all methods defined for a class? (e.g. all functions that operate on tables, say) Second question: my first dirty hack would be something like args <- list(...) table.sum <- args[[1]] for (i in 2:length(args)) table.sum <- table.sum + args[[i]] making use of the fact that `+` is defined for tables (and forgetting about cases where two tables don't feature the same names). It works, but isn't there a more elegant way to get the same? Last question: is there a way to determine the call stack, such that I can see the names of the function which are actually executed when I commit a command? I know a little about R's dispatching mechanism for S3 classes (plot(a) actually calls plot.table) but I've no clue which function is called if I type a + a (especially since `+` belongs to the generic function group Ops and I do not know at all whether its S4 or S3). I read the documentation about S3 Group Generic Functions and tried to delve into S4, but obviously I was not able to understand everything completely. So it would be great if somebody could help me out with this specific topic and point me to some resources where I can learn more. Thanks for your help in advance. BR, Thorn ______________________________________________ [hidden email] 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. [[alternative HTML version deleted]] ______________________________________________ [hidden email] 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. |
On Aug 23, 2010, at 12:39 PM, Thaler, Thorn, LAUSANNE, Applied Mathematics wrote: > Perfectly, works as expected. Regarding the other questions, can > anybody point me to the right direction? > > > > So first question: where is the `+` operation defined for tables? tables are a modification via attributes of matrices. > Is it > S4? How can I see the source code of S4 functions I don't think so, at least from reading: ?Arithmetic ?groupGeneric ?InternalMethods > (I'm not very > comfortable with S4)? Or in general how do I find all generic > functions > for a specific class? I can get all S3 implementations of plot with > methods(plot), I can get all S4 functions with getMethods(plot). But > I've no idea of how to find all methods defined for a class? (e.g. all > functions that operate on tables, say) > > Second question: my first dirty hack would be something like > > args <- list(...) > table.sum <- args[[1]] > for (i in 2:length(args)) table.sum <- table.sum + args[[i]] > > > making use of the fact that `+` is defined for tables (and forgetting > about cases where two tables don't feature the same names). It works, > but isn't there a more elegant way to get the same? Would sum() work better than "+"? The sum function is not a dyadic operator. (a <- table(rep(1:3, sample(10,3)))) k <- list(a,a,a) > Reduce(sum, k ) [1] 51 > do.call("sum", k) [1] 51 > > > Last question: is there a way to determine the call stack, such that I > can see the names of the function which are actually executed when I > commit a command? I know there is some feeling hereabouts that saying anything vaguely like RTFM (of RTFA's) is passe, but I do believe that you can find either the answer or pointers in the directions of an answer to this by reviewing the posting over this last weekend to a question about recovering from errors. (I was not the responder, so do not remember the subject line. Oh heck. .... search, search, search, ... there it is ... "on abort error, always show call stack?") > I know a little about R's dispatching mechanism for S3 > classes (plot(a) actually calls plot.table) but I've no clue which > function is called if I type a + a (especially since `+` belongs to > the > generic function group Ops and I do not know at all whether its S4 or > S3). I read the documentation about S3 Group Generic Functions and > tried > to delve into S4, Oh well. You've already been there. Maybe my advice above will help someone else. > but obviously I was not able to understand everything > completely. So it would be great if somebody could help me out with > this > specific topic and point me to some resources where I can learn more. > > Thanks for your help in advance. > > BR, > > Thorn David Winsemius, MD West Hartford, CT ______________________________________________ [hidden email] 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. |
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