Error in if (left == 0) break : argument is of length zero about multidplyr

[hadley]

Can you please provide a minimal reprex (reproducible example)? The goal of a reprex is to make it as easy as possible for me to recreate your problem so that I can fix it: please help me help you!

If you've never heard of a reprex before, start by reading "What is a reprex", and follow the advice further down the page.

[cwaldock1]

Have only run into the error once, and thought it might be a bug somewhere in multidplyr. The example is a similar scale to the data I was running at the time.

Cheers

## -- ## 
library(devtools)
install_github("mfasiolo/qgam")
library(qgam)
library(dplyr)
library(multidplyr)
library(purrr)

# Create tibble
# Groups
TestData <- as_data_frame(data.frame(Group1 = sort(as.factor(rep(1:3000, length.out = 6000))), 
                          Group2 = as.factor(rep(1:2))))

# Variables
TestData <- TestData %>% 
  group_by(Group1, Group2) %>% 
  do(x = seq(1:1000),
     y = rnorm(1000)) %>% 
  unnest(x,y)
                    
# Optional subset to smaller scale for speed. 
#TestData <- TestData[1:10000,]

#  Detect clusters
parallel::detectCores() # 4 cores

# Create groups
group <- rep(1:4, 
             length.out = nrow(TestData %>% group_by(Group1, Group2) %>% nest()))
TestData2 <- bind_cols(tibble(group), TestData %>% group_by(Group1, Group2) %>% nest())
TestData2 <- TestData2 %>% unnest(data)

# Create clusters
cluster <- create_cluster(cores = 4)

# Create partition dataframe
TestDataParty <- TestData2 %>% partition(group, cluster = cluster)

# Load library for within each cluster
cluster_library(TestDataParty, "qgam")

# Run models in parallel 
TestDataPartyOutput <- TestDataParty %>% group_by(Group1, Group2) %>% 
  do(Model1 = tryCatch(qgam(y ~ s(x, k = 3), qu = 0.95, data = .), error = function(e) NA),
     Model2 = tryCatch(qgam(y ~ s(x, k = 4), qu = 0.95, data = .), error = function(e) NA),
     Model3 = tryCatch(qgam(y ~ s(x, k = 5), qu = 0.95, data = .), error = function(e) NA),
     Model4 = tryCatch(qgam(y ~ s(x, k = 7), qu = 0.95, data = .), error = function(e) NA))

[mschilli87]

I ran into the same problem and 'resolved' it by re-initiating my cluster. I did not change any code, just re-ran the cluster setup (incl. library loading and data copying).

[hadley]

Seems unlikely to be a bug in multidplyr, but if you're still interested, and can create a simple reprex, please file a new issue.