From 0c98041fb7e45b613671d1eda2658e1fa1aa65cb Mon Sep 17 00:00:00 2001
From: Anil Goyal <73267890+anilyayavar@users.noreply.github.com>
Date: Sun, 28 Jul 2024 11:39:39 +0530
Subject: [PATCH] when you have groups of columns

when you have groups of columns that you want to compute with simultaneously.
---
 iteration.qmd | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/iteration.qmd b/iteration.qmd
index 62090c688..bbff172b5 100644
--- a/iteration.qmd
+++ b/iteration.qmd
@@ -393,7 +393,27 @@ df_long |>
   summarize(mean = weighted.mean(val, wts))
 ```
 
-If needed, you could `pivot_wider()` this back to the original form.
+If needed, you could `pivot_wider()` this back to the original form.  
+
+This problem was actually solved on StackOverflow much earlier to release of 2nd edition.
+
+```{r}
+df_paired |>
+  summarise(
+    across(
+      .cols = ends_with("val"),
+      .fns = ~ weighted.mean(., get(str_replace(
+        cur_column(), "val", "wts"
+      ))),
+      .names = '{str_remove(col, "_val")}'
+    )
+  )
+
+#>  # A tibble: 1 × 4
+#>       a     b      c      d
+#>   <dbl> <dbl>  <dbl>  <dbl>
+#> 1 0.180 0.199 -0.208 -0.746
+```
 
 ### Exercises