From a0770998d0bc062e18de572738b5b8357f2db147 Mon Sep 17 00:00:00 2001
From: piever <pietro.vertechi@neuro.fchampalimaud.org>
Date: Thu, 18 Jan 2018 14:14:29 +0000
Subject: [PATCH] group by more than one column

---
 README.md | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 8d40a7db9..fe9d09ec8 100644
--- a/README.md
+++ b/README.md
@@ -64,10 +64,26 @@ df |>
     @df scatter(:b, :d)
 ```
 
-The old syntax, passing the `DataFrame` as the first argument to the `plot` call is still supported, but has several limitations (the most important being incompatibility with user recipes):
+The `@df` syntax is also compatible with Plots grouping machinery:
+
+```julia
+using RDatasets
+school = RDatasets.dataset("mlmRev","Hsb82")
+@df school density(:MAch, group = :Sx)
+```
+
+To group by more than one column, use a tuple of symbols:
+
 ```julia
-plot(df, :a, [:b :c], colour = [:red :blue])
+@df school density(:MAch, group = (:Sx, :Sector), legend = :topleft)
 ```
+
+![grouped](https://user-images.githubusercontent.com/6333339/35101563-eacf9be4-fc57-11e7-88d3-db5bb47b08ac.png)
+
+---
+
+The old syntax, passing the `DataFrame` as the first argument to the `plot` call is no longer supported.
+
 ---
 
 ## marginalhist with DataFrames