added comments

module3/exo1/influenza-like-illness-analysis.ipynb

@@ -26,6 +26,13 @@
     "The data on the incidence of influenza-like illness are available from the Web site of the [Réseau Sentinelles](http://www.sentiweb.fr/). We download them as a file in CSV format, in which each line corresponds to a week in the observation period. Only the complete dataset, starting in 1984 and ending with a recent week, is available for download."
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**Observation**: We now have a local file with the data, so the following line has been commented out:"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 10,
@@ -57,6 +64,13 @@
     "The first line of the CSV file is a comment, which we ignore with `skip=1`."
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**Observation**: We modified and now we read the data from the file *raw_data.csv*:"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 11,