[Rd] Reduce: extra args wishlist?

[Ben Bolker]

  Is there a reason that Reduce() doesn't take a "..." argument that
would allow arbitrary extra arguments to be passed through to the function?

  Here is a little example of how this would be convenient:

z <- list(
          data.frame(state=c("California"),
                     cases=0),
          data.frame(state=c("California","Massachusetts"),
                     cases=c(1,2)),
          data.frame(state=c("California","Massachusetts","Arizona"),
                     cases=c(1,2,17)))

## read in revised version of Reduce()
Reduce(merge,z,by="state",all=TRUE)

  The change is simple -- just add "..." to every call to the function
in Reduce() --  patch is included below my signature ...

  It's not a big deal -- I could also do
Reduce(function(x,y) { merge(x,y,by="state",all=TRUE) }, z)
but there doesn't seem to be a good reason not to allow it ...

  cheers
    Ben Bolker


-- 
Ben Bolker
Associate professor, Biology Dep't, Univ. of Florida
bolker at ufl.edu / www.zoology.ufl.edu/bolker
GPG key: www.zoology.ufl.edu/bolker/benbolker-publickey.asc


*** /home/ben/funprog.R.new	2009-06-06 18:30:56.000000000 -0400
--- src/library/base/R/funprog.R	2009-02-12 10:39:32.000000000 -0500
***************
*** 15,21 ****
  #  http://www.r-project.org/Licenses/

  Reduce <-
! function(f, x, init, right = FALSE, accumulate = FALSE, ...)
  {
      mis <- missing(init)
      len <- length(x)
--- 15,21 ----
  #  http://www.r-project.org/Licenses/

  Reduce <-
! function(f, x, init, right = FALSE, accumulate = FALSE)
  {
      mis <- missing(init)
      len <- length(x)
***************
*** 47,57 ****
      if(!accumulate) {
          if(right) {
              for(i in rev(ind))
!                 init <- f(x[[i]], init, ...)
          }
          else {
              for(i in ind)
!                 init <- f(init, x[[i]], ...)
          }
          init
      }
--- 47,57 ----
      if(!accumulate) {
          if(right) {
              for(i in rev(ind))
!                 init <- f(x[[i]], init)
          }
          else {
              for(i in ind)
!                 init <- f(init, x[[i]])
          }
          init
      }
***************
*** 64,76 ****
              if(right) {
                  out[[len]] <- init
                  for(i in rev(ind)) {
!                     init <- f(x[[i]], init, ...)
                      out[[i]] <- init
                  }
              } else {
                  out[[1L]] <- init
                  for(i in ind) {
!                     init <- f(init, x[[i]], ...)
                      out[[i]] <- init
                  }
              }
--- 64,76 ----
              if(right) {
                  out[[len]] <- init
                  for(i in rev(ind)) {
!                     init <- f(x[[i]], init)
                      out[[i]] <- init
                  }
              } else {
                  out[[1L]] <- init
                  for(i in ind) {
!                     init <- f(init, x[[i]])
                      out[[i]] <- init
                  }
              }
***************
*** 78,91 ****
              if(right) {
                  out[[len]] <- init
                  for(i in rev(ind)) {
!                     init <- f(x[[i]], init, ...)
                      out[[i]] <- init
                  }
              }
              else {
                  for(i in ind) {
                      out[[i]] <- init
!                     init <- f(init, x[[i]], ...)
                  }
                  out[[len]] <- init
              }
--- 78,91 ----
              if(right) {
                  out[[len]] <- init
                  for(i in rev(ind)) {
!                     init <- f(x[[i]], init)
                      out[[i]] <- init
                  }
              }
              else {
                  for(i in ind) {
                      out[[i]] <- init
!                     init <- f(init, x[[i]])
                  }
                  out[[len]] <- init
              }


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