R: annotate() gives error in R - r

Question

I am new to R. I have to use POSTagger in my code. I am using openNLP with R. While trying following sample code (in Sample.R file):
library("NLP")
library("openNLP")
s <- paste(c("Pierre Vinken, 61 years old, will join the board as a ",
"nonexecutive director Nov. 29.\n",
"Mr. Vinken is chairman of Elsevier N.V., ",
"the Dutch publishing group."),
collapse = "")
s <- as.String(s)
sent_token_annotator <- Maxent_Sent_Token_Annotator()
a1 <- annotate(s, sent_token_annotator)
s[a1]
And running this code from R Console (Using source("Sample.R"))
I am getting following error:
Error in as.data.frame.default(x[[i]], optional = TRUE) :
cannot coerce class "c("Simple_POS_Tag_Annotator", "Annotator")" to a data.frame
Following is the output of traceback() command :
14: stop(gettextf("cannot coerce class \"%s\" to a data.frame", deparse(class(x))),
domain = NA)
13: as.data.frame.default(x[[i]], optional = TRUE)
12: as.data.frame(x[[i]], optional = TRUE)
11: data.frame(x = function (s, a = Annotation())
{
s <- as.String(s)
y <- f(s)
n <- length(y)
id <- .seq_id(next_id(a$id), n)
type <- rep.int("sentence", n)
if (is.Annotation(y)) {
y$id <- id
y$type <- type
}
else if (is.Span(y)) {
y <- as.Annotation(y, id = id, type = type)
}
else stop("Invalid result from underlying sentence tokenizer.")
if (length(i <- which(a$type == "paragraph"))) {
a <- a[i]
a$features <- lapply(annotations_in_spans(y, a), function(e) list(constituents = e$id))
y <- c(y, a)
}
y
}, check.names = FALSE, stringsAsFactors = FALSE)
10: eval(expr, envir, enclos)
9: eval(as.call(c(expression(data.frame), x, check.names = !optional,
stringsAsFactors = stringsAsFactors)))
8: as.data.frame.list(x[[i]], optional = TRUE, stringsAsFactors = stringsAsFactors)
7: as.data.frame(x[[i]], optional = TRUE, stringsAsFactors = stringsAsFactors)
6: data.frame(position)
5: annotate(s, sent_token_annotator) at sample.R#11
4: eval(expr, envir, enclos)
3: eval(ei, envir)
2: withVisible(eval(ei, envir))
1: source("sample.R")
What can be possibly wrong? I am using Rx64 3.1.1 on Windows 7. Any help will be much appreciated. Thanks in advance.

Answer 1

I have the same problem and i fixed it by removing/detach the ggplot2 package. There is a function called Annotate in ggplot2 and it is the same name in both packages. I suggest you make sure that it is looking at the correct function in the library... in my case it was looking at the Annotate function of ggplot2 and not the NLP package.

Answer 2

I don't have an exact answer but suffered the same error using NLP, openNLP, tm, qdap. I worked backward restarting R and loading (library) one package, running code, then loading another package and running code, until I ran across the "cannot coerce to a dataframe" error. I found, in my case that qdap interferes with the openNLP annotate() function call -- which is actually using an NLP wrapper.
openNLP version 0.2-3 imports NLP (≥ 0.1-2), openNLPdata (≥ 1.5.3-1), and rJava (≥ 0.6-3). Because you loaded NLP explicitly, it may be a case of two instances of NLP running in memory interfering with each other. Try just loading openNLP and running your code

Answer 3

Multiple packages have same name. If you specifically tell R which package to use it will probably resolve the issue. For example, instead of Arrange(...), try using openNLP::Arrange(...)