如何在Localytics的R httr查询中包含/排除filter语句

我可以使用R成功地从Localytics查询数据，例如以下示例：

r <- POST(url = "https://api.localytics.com/v1/query,
           body=list(app_id=<APP_ID>,
                     metrics=c("occurrences","users"),
                     dimensions=c('a:URI'),
                     conditions=list(day = c("between", "2020-02-11", "2020-03-12"),
                                     event_name = "Content Viewed",
                                     "a:Item URI" = "testing")
           ),
           encode="json",
           authenticate(Key,Secret),
           accept("application/json"),
           content_type("application/json"))
stop_for_status(r)

但是我尝试添加filterDim和filterCriteria只会产生错误不可处理的实体。请记住，我可以根据很多变量进行筛选，而不仅仅是：Item URI，因此我还需要能够对其进行操作

如何包含语句，如果需要筛选，可以合并该行，但如果不需要筛选，则不包括该行？

条件只是一个列表，因此可以有条件地向其中添加元素。在这里，我们只使用一个if语句来测试传递的值的数量，如果是，则将它们添加进来

get_localytics <- function(appID, metrics, dimensions, from = Sys.Date()-30, 
                           to = Sys.Date(), eventName = "Content Viewed",
                           Key, Secret, filterDim = NULL, filterCriteria = NULL){

  conditions <- list(day = c("between", as.character(from), as.character(to)),
                     event_name = eventName)
  if (!is.null(filterDim)  & !is.null(filterCriteria)) {
    conditions[[filterDim]] <- filterCriteria)
  }

  r <- httr::POST(url = "https://api.localytics.com/v1/query",
                  body = list(app_id = appID,
                              metrics = metrics,
                              dimensions = dimensions,
                              conditions = conditions),
                  encode="json",
                  authenticate(Key, Secret),
                  accept("application/json"),
                  content_type("application/json"))
  stop_for_status(r)
  result <- paste(rawToChar(r$content),collapse = "")  
  document <- fromJSON(result)                                      
  df <- document$results
  return(df)
}

get_localytics <- function(appID, metrics, dimensions, from = Sys.Date()-30, 
                           to = Sys.Date(), eventName = "Content Viewed",
                           Key, Secret, filterDim = NULL, filterCriteria = NULL){

  conditions <- list(day = c("between", as.character(from), as.character(to)),
                     event_name = eventName)
  if (!is.null(filterDim)  & !is.null(filterCriteria)) {
    conditions[[filterDim]] <- filterCriteria)
  }

  r <- httr::POST(url = "https://api.localytics.com/v1/query",
                  body = list(app_id = appID,
                              metrics = metrics,
                              dimensions = dimensions,
                              conditions = conditions),
                  encode="json",
                  authenticate(Key, Secret),
                  accept("application/json"),
                  content_type("application/json"))
  stop_for_status(r)
  result <- paste(rawToChar(r$content),collapse = "")  
  document <- fromJSON(result)                                      
  df <- document$results
  return(df)
}