docs: update

1 files changed, 8 insertions, 10 deletions

diff --git a/docs/online_duration.md b/docs/online_duration.md
index 22af4b1..6076d18 100644
--- a/docs/online_duration.md
+++ b/docs/online_duration.md
@@ -6,13 +6,12 @@ View/visualize the amount of time people spend online.
 Usage
 -----
 
-Run from the top-level directory using `python -m`.
-For example:
+Run from the top-level directory using `python -m`:
 
     > python -m bin.online_duration -h
     usage: online_duration.py [-h] [--grouping {user,date,weekday,hour}]
                               [--input-format {csv,log,null}]
-                              [--output-format {csv,json,img}] [--from DATE_FROM]
+                              [--output-format {csv,json,plot}] [--from DATE_FROM]
                               [--to DATE_TO]
                               input [output]
 
@@ -20,7 +19,6 @@ This script additionally requires [matplotlib] to be installed.
 
 Analyze the database produced by [track_status.py] and calculate the total
 amount of time people spent online.
-
 For example (assuming the database in "db.csv" was generated by
 [track_status.py] before):
 
@@ -109,23 +107,23 @@ Sunday,0:00:00
 ```
 
 In my opinion, the script's most useful feature is the ability to easily create
-plots that represent the text data (like in the examples above).
-To produce a plot, pass `img` as the `--output-format` parameter value and add
+plots that represent this data (like in the examples above).
+To produce a plot, pass `plot` as the `--output-format` parameter value and add
 a file path to write the image to.
 
-    > python -m bin.online_duration --output-format img db.csv user.png
+    > python -m bin.online_duration --output-format plot db.csv user.png
 
 ![user.png]
 
-    > python -m bin.online_duration --output-format img --grouping date db.csv date.png
+    > python -m bin.online_duration --output-format plot --grouping date db.csv date.png
 
 ![date.png]
 
-    > python -m bin.online_duration --output-format img --grouping weekday db.csv weekday.png
+    > python -m bin.online_duration --output-format plot --grouping weekday db.csv weekday.png
 
 ![weekday.png]
 
-    > python -m bin.online_duration --output-format img --grouping hour db.csv hour.png
+    > python -m bin.online_duration --output-format plot --grouping hour db.csv hour.png
 
 ![hour.png]