r - Function on data.table environment errors -

can explain me why bar doesn't work? bug in data.table?

circles<-data.table(radius=1:10)  foo<-function(circ){   circ[,diameter:=2*radius] } dput(x = foo,file = 'func.r') bar<-dget(file = 'func.r')  foo(circles)  bar(circles) 

it has fact dget function sets environment of object returns other .globalenv. there's easy enough work around, it'll drive rookie me nuts trying figure out why broke in first place.

mydget<-function(file){   temp<-dget(file=file)   environment(temp)<-.globalenv   return(temp) }  bar<-mydget(file = 'func.r') 

from dput:

if x function associated environment stripped. hence scoping information can lost.

parent.env(environment(bar)) # <environment: namespace:base> 

both foo(circles) , bar(circles) result in [.data.table getting dispatched, in case bar(), looking @ traceback():

traceback() # 6: stop("check is.data.table(dt) == true. otherwise, := , `:=`(...) defined use in j, once , in particular ways. see help(\":=\").") # 5: `:=`(diameter, 2 * radius) # 4: `[.data.frame`(x, i, j) # 3: `[.data.table`(circ, , `:=`(diameter, 2 * radius)) @ func.r#3 # 2: circ[, `:=`(diameter, 2 * radius)] @ func.r#3 # 1: bar(circles) 

as can see [.data.table dispatches [.data.frame. happens because of part within [.data.table:

if (!cedta()) {   # fix #5070 (to do)   nargs = nargs() - (!missing(drop))   ans = if (nargs<3l) `[.data.frame`(x,i) # drop ignored anyway df[i]   else if (missing(drop)) `[.data.frame`(x,i,j)   else `[.data.frame`(x,i,j,drop)   # added is.data.table(ans) check fix bug #5069   if (!missing(i) & is.data.table(ans)) setkey(ans,null) # see test 304   return(ans) } 

here !cedta() true in case of bar(). can confirm cedta issue setting options(datatable.verbose=true) , rerunning. get:

# cedta decided 'base' wasn't data.table aware 

so cedta() do?

suppose you're using data.table objects, , using package that's not aware of data.table data structure. , let's package has function called funa. , you're calling function follows:

funa(dt) 

now since package isn't data.table aware, using code follows:

funa <- function(...) {     ....     tmp <- dt[, cols]     .... } 

here dt[, cols] not work on data.table due minor differences in data.table's defaults (by default with = true). , data.table, we'd need dt[, cols, with=false].

for code work well, we've identify you're using data.table object on function package doesn't know how subset columns data.table (or in other words, not data.table aware).

and looking @ parent environment of function , gives namespace of package you're using (if you're using package), , check if package imports, or depends on data.table, or if it's 1 of packages we've whitelisted.

this case special (or strange) because function you defined has parent environment base, , namespace base isn't data.table aware.

therefore not bug.

?dget describes not way transfer objects between r sessions (under note section). saverds works fine , can use alternative (better) workaround:

saverds(foo, "func.rds") bar <-readrds("func.rds") bar(circles)  # works