在mclapply(content(x)， FUN，…)中:所有调度的内核在用户代码中遇到错误

Question

当我将下面的代码运行到倒数第二行时，我得到了警告消息:

在mclapply(content(x)， FUN，…)中:遇到的所有调度内核用户代码错误

当我运行最后一行时，我得到

" UseMethod("words")出错:n no applicable method for'words'应用于类"character"n"的对象attr(，"class")"try-error" attr(，"condition")

下面的链接是一个可复制的例子，我们可以将其复制/粘贴到R中并运行。

https://github.com/weijia2013/mclapply-issue/blob/master/codes

我刚开始学R，我会很感激你的帮助。

library(devtools)
install_github("twitteR", username="geoffjentry")
library(twitteR)
setup_twitter_oauth("API Key", "API Secret")
rdmTweets <- userTimeline('rdatamining', n=200)
(nDocs <- length(rdmTweets))
rdmTweets[11:15]
for (i in 11:15) {cat(paste("[[", i, "]] ", sep="")) + writeLines(strwrap(rdmTweets[[i]]$getText(), width=73))}
df <- do.call("rbind", lapply(rdmTweets, as.data.frame))
dim(df)
library(tm)
library(SnowballC)
library(RWeka)
library(rJava)
library(RWekajars)
myCorpus <- Corpus(VectorSource(df$text))
myCorpus <- tm_map(myCorpus, tolower)
myCorpus <- tm_map(myCorpus, removePunctuation)
myCorpus <- tm_map(myCorpus, removeNumbers)
removeURL <- function(x) gsub("http[[:alnum:]]*", "", x)
myCorpus <- tm_map(myCorpus, removeURL)
myStopwords <- c(stopwords("english"), "available", "via")
myStopwords <- setdiff(myStopwords, c("r", "big"))
myCorpus <- tm_map(myCorpus, removeWords, myStopwords)

myCorpusCopy <- myCorpus
myCorpus <- tm_map(myCorpus, stemDocument)
for (i in 11:15) {cat(paste("[[", i, "]] ", sep="")) + writeLines(strwrap(myCorpus[[i]], width=73))}
myCorpus <- tm_map(myCorpus, stemCompletion, dictionary=myCorpusCopy)
inspect(myCorpus[11:15])
sessionInfo()
R version 3.1.1 (2014-07-10)
Platform: x86_64-apple-darwin13.1.0 (64-bit)
locale:
[1] en_GB.UTF-8/en_GB.UTF-8/en_GB.UTF-8/C/en_GB.UTF-8/en_GB.UTF-8
attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods  
[7] base     
other attached packages:
[1] RWekajars_3.7.11-1 rJava_0.9-6        RWeka_0.4-23      
[4] SnowballC_0.5      tm_0.6             NLP_0.1-3         
[7] twitteR_1.1.8      devtools_1.5      
loaded via a namespace (and not attached):
[1] bit_1.1-12     bit64_0.9-4    digest_0.6.4   evaluate_0.5.5
[5] grid_3.1.1     httr_0.4       memoise_0.2.1  parallel_3.1.1
[9] RCurl_1.95-4.1 rjson_0.2.14   slam_0.1-32    stringr_0.6.2 
[13] tools_3.1.1    whisker_0.3-2 

Answer 1

尝试使用以下代码:

myCorpus <- tm_map(myCorpus, stemDocument,lazy=TRUE).
myCorpus <- tm_map(myCorpus, tolower,lazy=TRUE) etc.

我认为新的tm包明确要求这个

Answer 2

我尝试了@Charles Copley提供的解决方案，但在我的代码中不起作用。对于后来的谷歌搜索者，另一个替代解决方案是将核心数设置为1。

corpus = tm_map(corpus, tolower, mc.cores = 1)

这篇文章tm_map有parallel::mclapply在Mac上的错误提供了一个有用的解释