构建正确的 API 查询 URL，以按多个关键字从 clinicaltrials.gov 中筛选数据

问：

我正在尝试从公共 API 获取一些数据，并且需要一些帮助来找出请求 URL 的正确查询语法。

下面是我的剧本。（没关系修复或改进功能，到目前为止它运行良好。

我需要的是正确的查询 URL。

我想从 clinicaltrials.gov 获取搜索词“EGFR”的临床研究列表，但缩小搜索范围，以便仅返回“OverallStatus”字段中具有“Recruiting”或“Active，not recruiting”的结果。以下是“OverallStatus”字段的可能值。

我很难弄清楚 API 文档。有一个包含“搜索表达式”和“语法”的页面，但它们没有说明如何搜索多个值。如何构建查询字符串以在字段中搜索多个可能的值？

我很欣赏任何见解！

library(tidyverse)
library(httr)
library(jsonlite)
library(glue)


get_studies_df <- function(query_url){
  
  # get clinical studies data
  res <- httr::GET(query_url)
  
  if(!httr::status_code(res) == 200){
    #if request failed return empty data frame
    empty_df <- stats::setNames(data.frame(matrix(ncol = 5, nrow = 0)), c("Rank", "NCTId", "Condition", "BriefTitle", "OverallStatus"))
    return(empty_df)
  }
  
  # get data from response obj
  data <- httr::content(res, as="text", encoding = "UTF-8") %>%
    jsonlite::fromJSON()
  
  # prepare clinical studies data frame
  studies_df <- data$StudyFieldsResponse$StudyFields %>%
    # combine conditions if there is more than one
    dplyr::rowwise() %>%
    mutate(Condition = paste(Condition, collapse = ", ")) %>%
    dplyr::ungroup()
  # unlist data frame columns to show full length text
  for (i in c(1:ncol(studies_df))){
    studies_df[,i] <- unlist(studies_df[,i])
  }
  
  return(studies_df)
  
}
 

### here are all the query strings I tried ###

# get all studies for EGFR (WORKING, but finds 5000+ studies, way too many)
query_url <- "https://ClinicalTrials.gov/api/query/study_fields?expr=EGFR&fields=NCTId,Condition,BriefTitle,OverallStatus&fmt=json"

# get "Recruiting" studies only (WORKING)
query_url <- "https://ClinicalTrials.gov/api/query/study_fields?expr=EGFR+AREA[OverallStatus]+Recruiting&fields=NCTId,Condition,BriefTitle,OverallStatus&fmt=json"

# get "Active" studies only (WORKING)
query_url <- "https://ClinicalTrials.gov/api/query/study_fields?expr=EGFR+AREA[OverallStatus]+Active&fields=NCTId,Condition,BriefTitle,OverallStatus&fmt=json"

### I'm trying to get "Recruiting" OR "Active" studies. These are NOT WORKING ###

# returns only "Active"
query_url <- "https://ClinicalTrials.gov/api/query/study_fields?expr=EGFR+AREA[OverallStatus]+Recruiting+Active&fields=NCTId,Condition,BriefTitle,OverallStatus&fmt=json"

# returns nothing
query_url <- "https://ClinicalTrials.gov/api/query/study_fields?expr=EGFR+AREA[OverallStatus]+RANGE[Recruiting,Active]&fields=NCTId,Condition,BriefTitle,OverallStatus&fmt=json"

# returns only "Active"
query_url <- "https://ClinicalTrials.gov/api/query/study_fields?expr=EGFR+AREA[OverallStatus]+Recruiting+AREA[OverallStatus]+Active&fields=NCTId,Condition,BriefTitle,OverallStatus&fmt=json"

# returns everything ("Recruiting", "Completed", "Unknown status", "Active, not recruiting") ??
query_url <- "https://ClinicalTrials.gov/api/query/study_fields?expr=EGFR+AREA[OverallStatus]+Recruiting+OR+Active&fields=NCTId,Condition,BriefTitle,OverallStatus&fmt=json"


df <- get_studies_df(query_url)

输出表：