[GitHub] [arrow] lidavidm commented on a change in pull request #10724: ARROW-12964: [R] Add bindings for ifelse() and if_else()

[GitBox <gi...@apache.org>]

lidavidm commented on a change in pull request #10724:
URL: https://github.com/apache/arrow/pull/10724#discussion_r671402622



##########
File path: r/R/dplyr-functions.R
##########
@@ -634,20 +634,45 @@ nse_funcs$wday <- function(x, label = FALSE, abbr = TRUE, week_start = getOption
 }
 
 nse_funcs$log <- function(x, base = exp(1)) {
-  
+
   if (base == exp(1)) {
     return(Expression$create("ln_checked", x))
   }
-  
+
   if (base == 2) {
     return(Expression$create("log2_checked", x))
   }
-  
+
   if (base == 10) {
     return(Expression$create("log10_checked", x))
-  } 
+  }
   # ARROW-13345
   stop("`base` values other than exp(1), 2 and 10 not supported in Arrow", call. = FALSE)
 }
 
 nse_funcs$logb <- nse_funcs$log
+
+nse_funcs$if_else <- function(condition, true, false, missing = NULL){
+  if (!is.null(missing)) {
+    arrow_not_supported("missing argument")
+  }
+
+  # TODO: if_else doesn't yet support factors/dictionaries this can be removed when
+  # ARROW-13358 merges
+  warn_r_types <- is.factor(true) || is.factor(false)
+  # However, if they are expressions, we need to use the functions from nse_funcs
+  warn_expression_types_true <- inherits(true, "Expression") &&  nse_funcs$is.factor(true)
+  warn_expression_types_false <- inherits(false, "Expression") && nse_funcs$is.factor(false)
+
+  if (warn_r_types | warn_expression_types_true | warn_expression_types_false) {
+    warning("Factors are currently converted to chracters in if_else and ifelse", call. = FALSE)
+  }

Review comment:
       This is a more general issue (e.g. I believe all arithmetic kernels do the same thing). However for those kernels it's more unavoidable; for if_else and friends maybe we should implement specific dictionary handling.




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