From a0aa613c6ad5a3d482fe71122867bb4e49bb3a5d Mon Sep 17 00:00:00 2001
From: Richard Iannone <riannone@me.com>
Date: Tue, 4 May 2021 22:26:22 -0400
Subject: [PATCH] Create custom rounding function for `fmt_fraction()`

---
 R/format_data.R | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/R/format_data.R b/R/format_data.R
index 08e2987ce..a2cfd62fc 100644
--- a/R/format_data.R
+++ b/R/format_data.R
@@ -695,7 +695,7 @@ fmt_fraction <- function(data,
 
         # Round all values of x to the highest
         # granularity required for this formatter
-        x <- round(x, 3)
+        x <- round_gt(x, 3)
 
         # Divide the `x` values in 'big' and 'small' components
         big_x <- trunc(x)
@@ -827,7 +827,7 @@ get_frac_tbl <- function(accuracy, values) {
       stop("Unknown `accuracy` value.")
     )
 
-  values <- round(values, digits = digits)
+  values <- round_gt(values, digits = digits)
 
   lookup_fractions(lu_tbl = lu_tbl, values = values)
 }
@@ -875,7 +875,7 @@ lookup_fractions <- function(lu_tbl, values) {
 
     } else {
 
-      idx <- round(value, precision) == round(lu_tbl$value, precision)
+      idx <- round_gt(value, precision) == round_gt(lu_tbl$value, precision)
 
       if (!has_rounding) {
 
@@ -944,6 +944,19 @@ generate_fractions <- function(frac_tbl, layout, context) {
   fractions
 }
 
+# The `round_gt()` function is used in gt over `base::round()` for consistency
+# in rounding across R versions; it uses the 'Round-Half-Up' (R-H-U) algorithm,
+# which is *not* used in R >= 4.0
+round_gt <- function(x, digits = 0) {
+
+  x_sign <- sign(x)
+  z <- abs(x) * 10^digits
+  z <- 0.5 + z + sqrt(.Machine$double.eps)
+  z <- trunc(z)
+  z <- z / 10^digits
+  z * x_sign
+}
+
 #' Format values as currencies
 #'
 #' With numeric values in a **gt** table, we can perform currency-based