Add use of --compare with --all in README

README.md

@@ -285,7 +285,7 @@ To visualize your data, just run main.py with the ```-v``` or ```--visualize```
 - ```-c [<category> [<category> ...]]``` or ```--category [<category> [<category> ...]]``` to visualize all products in one or more categories
 - ```--id [<id> [<id> ...]]``` to visualize one or more products with the specified id(s)
 - ```-n [<name> [<name> ...]]``` or ```--name [<name> ...]]``` to visualize one or more products with the specified name(s)
-- ```--compare``` to compare two or more products with the specified id(s), name(s) and/or category(s) on one graph. Use with ```--id```, ```--name``` and/or ```--category```
+- ```--compare``` to compare two or more products with the specified id(s), name(s) and/or category(s) or all products on one graph. Use with ```--id```, ```--name```, ```--category``` and/or ```--all```
 
 ### Example graph
 ![](https://user-images.githubusercontent.com/57172157/171033112-908f6420-6c7a-44ef-ba67-8a4a73bbd96e.png)
@@ -359,7 +359,7 @@ python3 main.py -v -c <category> -utd
 
 **Compare two products**
 
-To compare two products on one graph, use the flag ```--compare``` with flag ```--id```, ```--name``` and/or ```--category``` , like so:
+To compare two products on one graph, use the flag ```--compare``` with flag ```--id```, ```--name```, ```--category``` and/or ```--all```, like so:
 ```
 python3 main.py -v --compare --id <id>
 ```
@@ -372,5 +372,8 @@ python3 main.py -v --compare --category <category>
 ```
 python3 main.py -v --compare --id <id> --name <name> --category <category>
 ```
+```
+python3 main.py -v --compare --all
+```
 
 ***OBS** when using ```--name``` or ```--category``` multiple products can be visualized*