Unknown error on Facebook API through R. - r

Question

I'm trying to download all the posts from a facebook page through RFacebook, but when the page has an high number of posts (over 400 or so), the script stops, returning the error
"Error in callAPI(url = url, token = token) : An unknown error has occurred." at the line where I call the getPage.
library(Rfacebook)
library(stringr)
load("fb_oauth")
token=fb_oauth
page<-getPage("bicocca", token, n = 100000, since = NULL, until = NULL, feed = TRUE)
noSpaceMsg<-str_replace_all(page$message, "[\r\n]" , "")
output<-as.data.frame(cbind(page$from_name,page$id, noSpaceMsg, page$created_time, page$type, page$link, page$likes_count, page$comments_count, page$shares_count))
colnames(output)<-c("username","msgid", "message", "created_time", "type", "link", "likes", "comments", "shares")
write.csv(output, "bicocca.csv", row.names=FALSE)
Where is the problem? How can I fix it?

Answer 1

It seems to be a problem with the API, not with the R package. When I try to do the query in the Graph API Explorer here, I get an error too. No idea why.
One way around this is to query month by month, wrapping the getPage function in a try command:
page <- 'bicocca'
dates <- seq(as.Date("2010/10/01"), as.Date("2015/04/20"), by="month")
n <- length(dates)-1
df <- list()
for (i in 1:n){
cat(as.character(dates[i]), " ")
try(df[[i]] <- getPage(page, token, since=dates[i], until=dates[i+1]))
cat("\n")
}
df <- do.call(rbind, df)
This will not give you all the posts, but probably most of them.