How to include / exclude filter statement in R httr query for Localytics - r

Question

I can successfully query data from Localytics using R, such as the following example:
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)
But what I would like to do is create a function so I can do this quickly and not have to copy/paste data.
The issue I am running into is with the line "a:Item URI" = "testing", where I am filtering all searches by the Item URI where they all equal "testing", but sometimes, I don't want to include the filter statement, so I just remove that line entirely.
When I wrote my function, I tried something like the following:
get_localytics <- function(appID, metrics, dimensions, from = Sys.Date()-30,
to = Sys.Date(), eventName = "Content Viewed",
Key, Secret, filterDim = NULL, filterCriteria = NULL){
r <- httr::POST(url = "https://api.localytics.com/v1/query",
body = list(app_id = appID,
metrics = metrics,
dimensions = dimensions,
conditions = list(day = c("between", as.character(from), as.character(to)),
event_name = eventName,
filterDim = filterCriteria)
),
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)
}
But my attempt at adding filterDim and filterCriteria only produce the error Unprocessable Entity. (Keep in mind, there are lots of variables I can filter by, not just "a:Item URI" so I need to be able to manipulate that as well.
How can I include a statement, where if I need to filter, I can incorporate that line, but if I don't need to filter, that line isn't included?

Answer 1

conditions is just a list, so you can conditionally add elements to it. Here we just use an if statement to test of the values are passed and if so, add them in.
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)
}