RCurl and postForm()
Hi Ryan postForm() is using a different style (or specifically Content-Type) of submitting the form than the curl -d command. Switching the style = 'POST' uses the same type, but at a quick guess, the parameter name 'a' is causing confusion and the result is the empty JSON array - "[]". A quick workaround is to use curlPerform() directly rather than postForm() r = dynCurlReader() curlPerform(postfields = 'Archbishop Huxley', url = 'http://www.datasciencetoolkit.org/text2people', verbose = TRUE, post = 1L, writefunction = r$update) r$value() This yields [1] "[{\"gender\":\"u\",\"first_name\":\"\",\"title\":\"archbishop\",\"surnames\":\"Huxley\",\"start_index\":0,\"end_index\":17,\"matched_string\":\"Archbishop Huxley\"}]" and you can use fromJSON() to transform it into data in R. D.
On 4/29/11 12:14 PM, Elmore, Ryan wrote:
Hi everybody, I think that I am missing something fundamental in how strings are passed from a postForm() call in R to the curl or libcurl functions underneath. For example, I can do the following using curl from the command line: $ curl -d "Archbishop Huxley" "http://www.datasciencetoolkit.org/text2people" [{"gender":"u","first_name":"","title":"archbishop","surnames":"Huxley","start_index":0,"end_index":17,"matched_string":"Archbishop Huxley"}] Trying the same thing, or what I *think* is the same thing (obvious not) in R (Mac OS 10.6.7, R 2.13.0) produces:
library(RCurl)
Loading required package: bitops
api <- "http://www.datasciencetoolkit.org/text2people" postForm(api, a="Archbishop Huxley")
[1] "[{\"gender\":\"u\",\"first_name\":\"\",\"title\":\"archbishop\",\"surnames\":\"Huxley\",\"start_index\":44,\"end_index\":61,\"matched_string\":\"Archbishop Huxley\"},{\"gender\":\"u\",\"first_name\":\"\",\"title\":\"archbishop\",\"surnames\":\"Huxley\",\"start_index\":88,\"end_index\":105,\"matched_string\":\"Archbishop Huxley\"}]"
attr(,"Content-Type")
charset
"text/html" "utf-8"
I can match the result given on the DSTK API's website by using system(), but doesn't seem like the R-like way of doing something.
system("curl -d 'Archbishop Huxley' 'http://www.datasciencetoolkit.org/text2people'")
158 141 141 141 0[{"gender":"u","first_name":"","title":"archbishop","surnames":"Huxley","start_index":0,"end_index":17,"matched_string":"Archbishop Huxley"}] 17 599 72 --:--:-- --:--:-- --:--:-- 670
If you want to see some additional information related to this question, I posted on StackOverflow a few days ago:
http://stackoverflow.com/questions/5797688/post-request-using-rcurl
I am working on this R wrapper for the data science toolkit as a way of illustrating how to make an R package for the Denver RUG and ran into this problem. Any help to this problem will be greatly appreciated by the Denver RUG!
Cheers,
Ryan
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