R/parse.R

In ropensci/IEEER: Interface to the IEEE Xplore Gateway

# convert XML result from IEEE_search to a list format
result2list <-
function(searchresult, sep="|")
{
    root <- XML::xmlRoot(XML::xmlParse(httr::content(searchresult, "text"), asText=TRUE))

    if(no_records(root)) {
        result <- NULL
        return(result)
    }

    totalfound <- as.numeric(XML::xmlValue(root[["totalfound"]]))
    totalsearched <- as.numeric(XML::xmlValue(root[["totalsearched"]]))

    result <- lapply(root["document"], record2vector, sep=sep)
    attr(result, "totalfound") <- totalfound
    attr(result, "totalsearched") <- totalsearched

    result
}

# convert XML for a single record to a named vector of character strings
record2vector <-
function(record, sep="|")
{
    nam <- names(record)
    nfield <- length(nam)
    len_field <- sapply(record[1:nfield], XML::xmlSize)

    res <- rep("", nfield)
    names(res) <- nam
    res[len_field==1] <- sapply(record[len_field==1], XML::xmlValue)
    for(i in which(len_field > 1))
        res[i] <- paste(sapply(record[[i]][1:len_field[i]], XML::xmlValue), collapse=sep)
    res
}

# expected columns in output
#   results will contain all of these
expected_columns <-
function()
{
    c("rank",
      "title",
      "authors",
      "affiliations",
      "pubtitle",
      "punumber",
      "py",
      "volume",
      "issue",
      "part",
      "spage",
      "epage",
      "arnumber",
      "abstract",
      "doi",
      "mdurl",
      "pdf",
      "pubtype",
      "publisher",
      "isbn",
      "issn",
      "publicationId",
      "thesaurusterms",
      "controlledterms",
      "uncontrolledterms",
      "htmlFlag")
}

# data frame for an empty result
empty_result <-
function(columns=expected_columns())
{
    result <- lapply(columns, function(a) character(0))
    names(result) <- columns
    as.data.frame(result)
}

# convert list of results (from result2list) into data.frame
#   test for this in tests/testthat/test-clean.R
listresult2df <-
function(listresult)
{
    n_result <- length(listresult)

    if(n_result==0)
        return(empty_result())

    columns <- expected_columns()

    # names of all fields in input
    allcol <- unique(unlist(lapply(listresult, names)))
    m <- match(allcol, columns)
    # add any unexpected ones to the vector of columns
    if(any(is.na(m)))
        columns <- c(columns, allcol[is.na(match(allcol, columns))])

    # empty data frame to contain result
    result <- matrix("", nrow=n_result, ncol=length(columns))
    dimnames(result) <- list(1:n_result, columns)
    result <- as.data.frame(result, stringsAsFactors=FALSE)

    # grab info for one column at a time
    #     missing values made empty character strings
    for(i in columns)
        result[,i] <- sapply(listresult, function(a) ifelse(i %in% names(a), a[i], ""))

    # copy over the attributes
    for(s in c("totalfound", "totalsearched"))
        attr(result, s) <- attr(listresult, s)

    result
}

no_records <-
function(root)
{
    val <- XML::xmlValue(root)

    if(length(grep("returned 0 records", val)) > 0 ||
       length(grep("No value specified for query parameter", val)) > 0 ||
       length(grep("One of the parameters .+ required", val)) > 0)
        return(TRUE)

    FALSE
}