How to write an R function which assigns to the object of the calling environment? -

i have objects of class contain several matrices, , build function access , possibly modifies subset of such matrix. example:

foo<-list(x=diag(1:4),y=matrix(1:8,2,4)) class(foo)<-"bar" attr(foo,"m")<-4 attr(foo,"p")<-2 rownames(foo$x)<-colnames(foo$x)<-colnames(foo$y)<-c("a.1","b.1","b.2","c.1") attr(foo,"types")<-c("a","b","b","c") 

now access , modify elements this:

foo$x[attr(foo,"types")%in%c("c","b"),attr(foo,"types")%in%c("c","b")]     foo$x[attr(foo,"types")%in%c("c","b"),attr(foo,"types")%in%c("c","b")]<-matrix(5,3,3) 

but instead of above, construct following type of function:

modify<-function(object,element,types){   # check object proper class,    # , element , types found in object    # returns local copy of corresponding subset:    object[[element]][attr(object,"types")%in%types,attr(object,"types")%in%types]      } 

for accessing above function ok, if want modify original object? doesn't work:

modify(foo,"x",c("c","b"))<-matrix(5,3,3) error in modify(foo, "x", c("c", "b")) <- matrix(5, 3, 3) :    not find function "modify<- 

is possible work somehow? if not, 1 option think of adding argument replace.with function modify , making assignment first local copy , copying change object in calling environment using assign function. need find original object in calling environment, i'm not sure how that.

with caveat frowned upon, can use following:

from target environment, set variable environment , pass argument function can use in assign, get etc

en <- environment() myfunc <- function(..., en=en) {   . etc .   assign("varname", envir=en) } 

note if changing attributes, setattr function of data.table package implements quote nicely:

 setattr(x,name,value)