diff --git a/cookbook/Chapter 4 - Find out on which weekday people bike the most with groupby and aggregate.ipynb b/cookbook/Chapter 4 - Find out on which weekday people bike the most with groupby and aggregate.ipynb
index 186a7094b..212fd35d1 100644
--- a/cookbook/Chapter 4 - Find out on which weekday people bike the most with groupby and aggregate.ipynb	
+++ b/cookbook/Chapter 4 - Find out on which weekday people bike the most with groupby and aggregate.ipynb	
@@ -348,7 +348,7 @@
     }
    ],
    "source": [
-    "berri_bikes.loc[:,'weekday'] = berri_bikes.index.weekday\n",
+    "berri_bikes['weekday'] = berri_bikes.index.weekday\n",
     "berri_bikes[:5]"
    ]
   },
@@ -367,7 +367,7 @@
     "\n",
     "Dataframes have a `.groupby()` method that is similar to SQL groupby, if you're familiar with that. I'm not going to explain more about it right now -- if you want to to know more, [the documentation](http://pandas.pydata.org/pandas-docs/stable/groupby.html) is really good.\n",
     "\n",
-    "In this case, `berri_bikes.groupby('weekday').aggregate(sum)` means \"Group the rows by weekday and then add up all the values with the same weekday\"."
+    "In this case, `berri_bikes.groupby('weekday').sum()` means \"Group the rows by weekday and then add up all the values with the same weekday\"."
    ]
   },
   {
@@ -454,7 +454,7 @@
     }
    ],
    "source": [
-    "weekday_counts = berri_bikes.groupby('weekday').aggregate(sum)\n",
+    "weekday_counts = berri_bikes.groupby('weekday').sum()\n",
     "weekday_counts"
    ]
   },
@@ -634,10 +634,10 @@
     "                    index_col='Date')\n",
     "# Add the weekday column\n",
     "berri_bikes = bikes[['Berri 1']].copy()\n",
-    "berri_bikes.loc[:,'weekday'] = berri_bikes.index.weekday\n",
+    "berri_bikes['weekday'] = berri_bikes.index.weekday\n",
     "\n",
     "# Add up the number of cyclists by weekday, and plot!\n",
-    "weekday_counts = berri_bikes.groupby('weekday').aggregate(sum)\n",
+    "weekday_counts = berri_bikes.groupby('weekday').sum()\n",
     "weekday_counts.index = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']\n",
     "weekday_counts.plot(kind='bar')"
    ]