Update influenza-like-illness-analysis.Rmd

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

@@ -26,6 +26,15 @@ The data on the incidence of influenza-like illness are available from the Web s
 data_url = "http://www.sentiweb.fr/datasets/incidence-PAY-3.csv"
 ```
 
+In order to protect us in case the Réseau Sentinelles Web server disappears or is modified, we make a local copy of this dataset that we store together with our analysis. It is unnecessary and even risky to download the data at each execution, because in case of a malfunction we might be replacing our file by a corrupted version. Therefore we download the data only if no local copy exists.	
+
+```{r}	
+data_file = "syndrome-grippal.csv"	
+if (!file.exists(data_file)) {	
+    download.file(data_url, data_file, method="auto")	
+}	
+```
+
 This is the documentation of the data from [the download site](https://ns.sentiweb.fr/incidence/csv-schema-v1.json):
 
 | Column name  | Description                                                                                                               |
@@ -41,11 +50,11 @@ This is the documentation of the data from [the download site](https://ns.sentiw
 | `geo_insee`  | Identifier of the geographic area, from INSEE https://www.insee.fr                                                        |
 | `geo_name`   | Geographic label of the area, corresponding to INSEE code. This label is not an id and is only provided for human reading |
 
-### Download
+### Reading the daa
 
 The first line of the CSV file is a comment, which we ignore with `skip=1`.
 ```{r}
-data = read.csv(data_url, skip=1)
+data = read.csv(data_file, skip=1)
 ```
 
 Let's have a look at what we got: