Can't access additional packages in futuremice

[tarensanders]

If you are trying to use mice with a method provided by an add-on package (e.g., "2l.pmm" from the {miceadds} package), the methods don't seem to be available in parallel. That is, they aren't passed into future_map, and so aren't available on the workers.

Here's an example (modified from the miceadds docs.

library(mice)
#> 
#> Attaching package: 'mice'
#> The following object is masked from 'package:stats':
#> 
#>     filter
#> The following objects are masked from 'package:base':
#> 
#>     cbind, rbind
library(miceadds)
#> * miceadds 3.16-18 (2023-01-06 10:54:00)

set.seed(976)
G <- 30        # number of groups
n <- 8        # number of persons per group
iccx <- .2    # intra-class correlation X
iccy <- .3    # latent intra-class correlation binary outcome
bx <- .4    # regression coefficient
threshy <- stats::qnorm(.70)  # threshold for y
x <- rep( rnorm( G, sd=sqrt( iccx) ), each=n )  +
            rnorm(G*n, sd=sqrt( 1 - iccx) )
y <- bx * x + rep( rnorm( G, sd=sqrt( iccy) ), each=n )  +
                rnorm(G*n, sd=sqrt( 1 - iccy) )
y <- 1 * ( y > threshy )
dat <- data.frame( group=100+rep(1:G, each=n), x=x, y=y )

#* create some missings
dat1 <- dat
dat1[ seq( 1, G*n, 3 ),"y" ]  <- NA
dat1[ dat1$group==2, "y" ] <- NA

vars <- colnames(dat1)
V <- length(vars)
#* predictor matrix
predmat <- matrix( 0, nrow=V, ncol=V)
rownames(predmat) <- colnames(predmat) <- vars
predmat["y", ] <- c(-2,2,0)
#* imputation methods
impmeth <- rep("",V)
names(impmeth) <- vars
#** imputation with predictive mean matching ('2l.pmm')
impmeth["y"] <- "2l.pmm"

imp1 <- mice::mice(
  data = as.matrix(dat1), method = impmeth,
  predictorMatrix = predmat, maxit = 1, m = 5
)
#> 
#>  iter imp variable
#>   1   1  y
#> Loading required namespace: lme4
#> boundary (singular) fit: see help('isSingular')
#> 
#>   1   2  y
#> boundary (singular) fit: see help('isSingular')
#> 
#>   1   3  y
#> boundary (singular) fit: see help('isSingular')
#> 
#>   1   4  y
#> boundary (singular) fit: see help('isSingular')
#> 
#>   1   5  y
#> boundary (singular) fit: see help('isSingular')

imp2  <- mice::futuremice(
   data = as.matrix(dat1), method = impmeth,
  predictorMatrix = predmat, maxit = 1, m = 5, n.core = 2
)
#> Error:
#> ℹ In index: 1.
#> Caused by error in `get()`:
#> ! object 'mice.impute.2l.pmm' not found

#> Backtrace:
#>      ▆
#>   1. ├─parallel (local) workRSOCK()
#>   2. │ └─parallel:::workLoop(...)
#>   3. │   └─parallel:::workCommand(master)
#>   4. │     ├─base::tryCatch(...)
#>   5. │     │ └─base (local) tryCatchList(expr, classes, parentenv, handlers)
#>   6. │     │   └─base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
#>   7. │     │     └─base (local) doTryCatch(return(expr), name, parentenv, handler)
#>   8. │     ├─base::tryCatch(...)
#>   9. │     │ └─base (local) tryCatchList(expr, classes, parentenv, handlers)
#>  10. │     │   └─base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
#>  11. │     │     └─base (local) doTryCatch(return(expr), name, parentenv, handler)
#>  12. │     ├─base::do.call(msg$data$fun, msg$data$args, quote = TRUE)
#>  13. │     └─future (local) `<fn>`(...)
#>  14. │       └─base::eval(expr, envir = envir, enclos = enclos)
#>  15. │         └─base::eval(expr, envir = envir, enclos = enclos)
#>  16. ├─base::tryCatch(...)
#>  17. │ └─base (local) tryCatchList(expr, classes, parentenv, handlers)
#>  18. │   └─base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
#>  19. │     └─base (local) doTryCatch(return(expr), name, parentenv, handler)
#>  20. ├─base::withCallingHandlers(...)
#>  21. ├─base::withVisible(...)
#>  22. ├─base::local(...)
#>  23. │ └─base::eval.parent(substitute(eval(quote(expr), envir)))
#>  24. │   └─base::eval(expr, p)
#>  25. │     └─base::eval(expr, p)
#>  26. ├─base::eval(...)
#>  27. │ └─base::eval(...)
#>  28. │   ├─base::withCallingHandlers(...)
#>  29. │   ├─base::do.call(...furrr_map_fn, args)
#>  30. │   └─purrr (local) `<fn>`(.x = 3L, .f = `<fn>`)
#>  31. │     └─purrr:::map_("list", .x, .f, ..., .progress = .progress)
#>  32. │       ├─purrr:::with_indexed_errors(...)
#>  33. │       │ └─base::withCallingHandlers(...)
#>  34. │       ├─purrr:::call_with_cleanup(...)
#>  35. │       └─.f(.x[[i]], ...)
#>  36. │         └─mice (local) ...furrr_fn(...)
#>  37. │           └─mice::mice(...)
#>  38. │             └─mice:::sampler(...)
#>  39. │               └─mice:::handles.format(paste0("mice.impute.", theMethod))
#>  40. │                 └─base::get(fn)
#>  41. └─base::.handleSimpleError(...)
#>  42.   └─purrr (local) h(simpleError(msg, call))
#>  43.     └─cli::cli_abort(...)
#>  44.       └─rlang::abort(...)

^{Created on 2023-03-30 with reprex v2.0.2}

As you can see, imp1 is fine, but imp2 using futuremice can't find the method.

The solution would seem to be to just pass in additional packages here: https://github.com/amices/mice/blob/3e3e3ca0fa53f1b90fb7142bedf36375d5282e90/R/futuremice.R#L162

Happy to make a PR with this change.

[thomvolker]

Thanks for posting the issue and providing a (probably the) solution!

This is a known issue (related to #529), because this also happens for user-defined imputation functions, we are working for a slightly more generic solution (probably this in combination with a globals argument in future_map()), but some verification and checks need to be done still.

[tarensanders]

Ah you're right that just passing in packages wouldn't help for user-defined functions. Let me know if there's a way you'd like me to contribute.

[stefvanbuuren]

Closing because of #550