这是我所得到的。我收到“400 Not Authorized”，可能是因为我的 openpaths 帐户没有连接到foursquare，也可能是代码有问题。请尝试一下！
所需软件包：
library(RCurl)
library(digest)
library(base64)
一些功能借用/改编自ROAuth：
## Get a random sequence of characters.
## Nonce - number used only once.
genNonce <- function(len = 15L + sample(1:16, 1L)) {
els <- c(letters, LETTERS, 0:9, "_")
paste(sample(els, len, replace = TRUE), collapse = "")
}
## this function is derived from utils::URLencode
## Characters not in the unreserved character set ([RFC3986] section 2.3) MUST be encoded
## unreserved = ALPHA, DIGIT, '-', '.', '_', '~'
## cf. http://oauth.net/core/1.0/#encoding_parameters
encodeURI <- function(URI, ...) {
if (!is.character(URI)) {
URI
} else {
OK <- "[^-A-Za-z0-9_.~]"
x <- strsplit(URI, "")[[1L]]
z <- grep(OK, x)
if (length(z)) {
y <- sapply(x[z], function(x) paste("%", toupper(as.character(charToRaw(x))),
sep = "", collapse = ""))
x[z] <- y
}
paste(x, collapse = "")
}
}
## we escape the values of the parameters in a special way that escapes
## the resulting % prefix in the escaped characters, e.g. %20 becomes
## %2520 as %25 is the escape for %
## cf. http://tools.ietf.org/html/rfc5849#section-3.4.1.3.2
normalizeParams <- function(params, escapeFun) {
names(params) <- sapply(names(params), escapeFun, post.amp = TRUE)
params <- sapply(params, escapeFun, post.amp = TRUE)
## If two or more parameters share the same name, they are sorted by their value.
params <- params[order(names(params), params)]
return(paste(names(params), params, sep = "=", collapse = "&"))
}
## From Ozaki Toru's code at https://gist.github.com/586468
signWithHMAC <- function(key, data) {
blockSize <- 64
hashlength <- 20
innerpad <- rawToBits(as.raw(rep(0x36, blockSize)))
outerpad <- rawToBits(as.raw(rep(0x5C, blockSize)))
zero <- rep(0 ,64)
HexdigestToDigest <- function(digest) {
as.raw(strtoi(substring(digest, (1:hashlength)*2-1,
(1:hashlength)*2), base=16))
}
mac <- function(pad, text) {
HexdigestToDigest(digest(append(packBits(xor(key, pad)), text),
algo='sha1', serialize=FALSE))
}
if(nchar(key) >= 64) {
keyDigested <- digest(key, algo="sha1", serialize=FALSE)
key <- intToUtf8(strtoi(HexdigestToDigest(keyDigested), base=16))
}
key <- rawToBits(as.raw(append(utf8ToInt(key), zero)[1:blockSize]))
base64(mac(outerpad, mac(innerpad, charToRaw(data))))[1]
}
## Sign an request made up of the URL, the parameters as a named character
## vector the consumer key and secret and the token and token secret.
signRequest <- function(uri, consumerKey, consumerSecret, params=character(),
oauthKey = "", oauthSecret = "", httpMethod = "GET",
nonce = genNonce(),
timestamp = Sys.time()) {
httpMethod <- toupper(httpMethod)
params["oauth_nonce"] <- nonce
params["oauth_timestamp"] <- as.integer(timestamp)
params["oauth_consumer_key"] <- consumerKey
params["oauth_signature_method"] <- 'HMAC-SHA1'
params["oauth_version"] <- '1.0'
if(oauthKey != "") params["oauth_token"] <- oauthKey
odat <- paste(
encodeURI(httpMethod), encodeURI(uri),
encodeURI(normalizeParams(params, encodeURI), post.amp = TRUE),
sep = "&"
)
okey <- encodeURI(consumerSecret)
if(oauthSecret != "") okey <- paste(okey, encodeURI(oauthSecret), sep = "&")
params["oauth_signature"] <- signWithHMAC(okey, odat)
return(params)
}
现在此函数尝试在 openpaths 网站上复制示例：
openpaths <- function(
access_key=getOption("openpaths.access_key"),
secret_key=getOption("openpaths.secret_key"),
curl=getCurlHandle()) {
uri <- 'https://openpaths.cc/api/1'
params <- signRequest(uri, consumerKey=access_key, consumerSecret=secret_key)
oa_header <- paste(names(params), params, sep="=", collapse=",")
ret <- getURL(
uri,
curl=curl,
.opts=list(
header=TRUE,
verbose=TRUE,
httpheader=c(Authorization=paste("OAuth ", oa_header, sep="")),
ssl.verifypeer = TRUE,
ssl.verifyhost = TRUE,
cainfo = system.file("CurlSSL", "cacert.pem", package = "RCurl")
)
)
return(ret)
}