Programmatic subsetting of a data.table in R -

this feels simple question solution has eluded me 90 minutes of trying, searching , reading manuals , online.

say i've got data.table:

dt<-data.table(a=runif(n = 10),b=runif(n = 10),c=runif(n = 10)) 

clearly works:

dt[a > 0.5] 

and gives me subset of dt values in column "a" greater 0.5. if want bit more flexible (because subset embedded in larger routine).

what i'd make proto-function work:

flexsubset<-function(scolumntosubset,dmin){ subs<-dt[scolumntosubset>dmin] return(subs) } 

i've tried without success, among many others...

with=false 

any suggestions? many time in advance!

if want pass string, this:

flexsubset = function(scolumntosubset, dmin)                 dt[get(scolumntosubset) > dmin]  flexsubset("a", 0.5) 

if want pass unevaluated expression, then:

flexsubset = function(scolumntosubset, dmin) {                 lhs = substitute(scolumntosubset)                 dt[eval(lhs) > dmin]              }  flexsubset(a, 0.5) flexsubset(a / b, 0.5)