R/findzebra.R

In rrrlw/webddx: Interact with Online Differential Diagnosis-Generating Tools

# uses JSON format to interact with FindZebra API
#####FINDZEBRA API CLIENT FUNCTIONALITY#####
#' Query FindZebra for differential diagnosis generation
#' 
#' Queries the FindZebra website and returns a data frame containing properly
#' formatted results, including the relevant rare medical conditions and
#' associated genes.
#' 
#' See FindZebra API <http://www.findzebra.com/about> for more information.
#' 
#' @param query a character vector in which each symptom is an element and
#' multiple words within a symptom are separated by spaces
#' @param num_rows  maximum number of desired rare conditions
#' @param fields  character vector containing a subset of the following:
#' `display_title`, `content`, `associated_gene`, `symptom`, `retrieved_date`,
#' `source_url`, `source`, `cui`, `score`.
#' @return data frame with 1 row per rare condition and 1 column per field
#' (see `fields` parameter)
#' @export
#' @examples 
#' \dontrun{
#' query_fz(query = c("muscle pain", "fatigue"))
#' }
query_fz <- function(query, num_rows = 20, fields = c("display_title",
                                                      "symptom",
                                                      "retrieved_date",
                                                      "source",
                                                      "score")) {
  # base URL for API with JSON format
  base_url <- "http://www.findzebra.com/api/call/json/query?"

  # make sure parameters are correctly formatted
  # at least length 1 for each
  valid_fields <- c("display_title", "content", "associated_gene", "symptom",
                    "retrieved_date", "source_url", "source", "cui", "score")
  if (length(query) < 1) {
    stop("Cannot have an empty query")
  }
  if (length(fields) < 1) {
    stop("Cannot have empty fields")
  } else if (sum(fields %in% valid_fields) < length(fields)) {
    stop(paste("Invalid field included. See fields parameter under",
               "?query_fz for more information."))
  }
  num_rows <- as.integer(num_rows)
  if (num_rows < 1) {
    stop("Cannot ask for less than 1 row of data")
  }
  # query must have only alphabetic and space chars
  # fields all elements must be from fixed list that FZ API accepts

  # format params correctly for URL - separate words in term with '+' and separate terms with '%2C+'
  query_corr <- paste(gsub(pattern = " ", replacement = "+", query, fixed = TRUE),
                      collapse = "%2C+")
  fields_corr<- paste(fields, collapse = ",%20")

  # build url request from FZ API
  query_url <- paste(base_url,
                     "q=",
                     query_corr,
                     "&fl=",
                     fields_corr,
                     "&rows=",
                     num_rows, sep = "")
  #print(query_url)

  # get JSON from FZ
  query_json <- jsonlite::fromJSON(query_url)

  # return JSON
  query_json$response$docs
}