define multiple aggregation functions outside of dcast and refer to them inside of dcast

[smidelius]

I want to define multiple aggregation functions in custom number/order outside of dcast and then pass it to dcast fun parameter.

I try to achieve something like that:

dt <-  data.table(x=sample(5,20,TRUE), y=sample(2,20,TRUE), 
                z=sample(letters[1:2], 20,TRUE), d1 = runif(20), d2=1L)

functions <- list(sum,mean)

dcast(dt, x + y ~ z, fun=functions, value.var="d1") 

But I get the error message:

Error in eval(expr, envir, enclos) : could not find function "functions"

[franknarf1]

Related to this SO question and issue #1369.

[arunsrinivasan]

dup of #1369