rforeachparallel-foreachrparallel

Getting an error in using foreach in R - no applicable method for 'filter' applied to an object of class "list"

I am getting in using foreach. Can someone please explain the reason.

Error in UseMethod("filter") : 
  no applicable method for 'filter' applied to an object of class "list"

library(dplyr)
library(doFuture)
library(foreach)

# PARALLEL PROCESSING
registerDoFuture()
plan(multicore, workers = 1)

tbl <- tibble(id = 1:10)

res <- foreach(ID = 1:10) %do%
  tbl %>% filter(id == ID)

# it simply works with for loop
l = list()
for (ID in 1:10)
{
  l[[ID]] <- tbl %>% filter(id == ID)
}
Solution

  • You need to be careful of operator precedence here. Enclose your loop body here in braces to be clear

    res <- foreach(ID = 1:10) %do%
  { tbl %>% filter(id == ID) }

    Otherwise you are running

    res <- (foreach(ID = 1:10) %do% tbl) %>% 
  filter(id == ID)

    which isn't what you seem to want in this case.