diff --git a/.gitignore b/.gitignore
index 423987e..9ea0c82 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 /secret/*.txt
 /data/*.xml
-/src/__pycache__/
 /plot/*.png
+
+__pycache__/
diff --git a/.idea/other.xml b/.idea/other.xml
new file mode 100644
index 0000000..a708ec7
--- /dev/null
+++ b/.idea/other.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="PySciProjectComponent">
+    <option name="PY_SCI_VIEW_SUGGESTED" value="true" />
+  </component>
+</project>
\ No newline at end of file
diff --git a/Dockerfile b/Dockerfile
index 39d04d1..43769ad 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,6 +2,10 @@ FROM python:3.8-alpine
 
 WORKDIR /usr/src/
 
+# setting the correct timezone requires "zdtata"
+# numpy (dependency of matplotlib) requires "make automake gcc ..."
+#   source: https://stackoverflow.com/a/48349161/6334421
+# pillow (dependency of matplotlib) requires "zlib-dev jpeg-dev ..."
 RUN apk update && \
     apk add \
         tzdata \
@@ -14,13 +18,7 @@ RUN apk update && \
 ENV TZ=Europe/Berlin
 RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
 
-# TODO
-#COPY requirements.txt ./
-#RUN pip3 install --no-cache-dir -r requirements.txt
-
-# numpy (dependency of matplotlib)
-# requires "make automake gcc ..."
-# source: https://stackoverflow.com/a/48349161/6334421
+RUN python3 -m pip install --no-cache-dir --upgrade pip
 
 # LDFLAGS required for "pip install pillow"
 # otherwise this would be necessary:
@@ -29,15 +27,19 @@ RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
 # source: https://github.com/python-pillow/Pillow/issues/3103#issuecomment-382634946
 ENV LDFLAGS=-L/usr/lib/x86_64-linux-gnu/
 
-RUN python3 -m pip install --no-cache-dir --upgrade pip
-RUN python3 -m pip install --no-cache-dir --upgrade requests
-RUN python3 -m pip install --no-cache-dir --upgrade setuptools
-RUN python3 -m pip install --no-cache-dir --upgrade numpy
-RUN python3 -m pip install --no-cache-dir --upgrade pillow
-RUN python3 -m pip install --no-cache-dir --upgrade matplotlib
+COPY requirements.txt ./
+RUN python3 -m pip install --no-cache-dir --upgrade -r requirements.txt
+#
+# if the above fails, try using the below instead
+#
+#RUN python3 -m pip install --no-cache-dir --upgrade requests
+#RUN python3 -m pip install --no-cache-dir --upgrade setuptools
+#RUN python3 -m pip install --no-cache-dir --upgrade numpy
+#RUN python3 -m pip install --no-cache-dir --upgrade pillow
+#RUN python3 -m pip install --no-cache-dir --upgrade matplotlib
 
-COPY ./src/ ./
-RUN chmod +x ./langfingaz/main.py
+COPY src/ ./
+RUN chmod +x langfingaz/main.py
 
 # unbuffered output option otherwise script sleeps before any output appears
 # python -u
diff --git a/README.md b/README.md
index e665a27..559fc0a 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,14 @@ Save these two values in the first line of the following files:
 
 ## run
 
+Start logging in the background:
+
+```shell
+docker-compose up -d
 ```
-docker-compose build
-docker-compose up
+
+Generate a new plot with the saved data:
+
+```shell
+sudo docker-compose run bbb-status plot
 ```
diff --git a/src/langfingaz/plotMeetings.py b/src/langfingaz/plotMeetings.py
index 1799711..9e91219 100644
--- a/src/langfingaz/plotMeetings.py
+++ b/src/langfingaz/plotMeetings.py
@@ -40,7 +40,12 @@ def doPlotMeetings(bbbStati: List[BbbStatus]) -> Path:
         voices.append(bbbStatus.voiceParticipantCount)
 
     # Note that even in the OO-style, we use `.pyplot.figure` to create the figure.
-    fig, ax = plt.subplots()  # Create a figure and an axes.
+    _a, _b = plt.subplots()  # Create a figure and an axes.
+    fig: plt.Figure = _a
+    ax = _b  # of type plt.axes.Axes ??
+    if not (issubclass(type(fig), plt.Figure)):
+        raise ValueError("expected Figure")
+
     ax.plot(time, participants, label='participants')  # Plot some data on the axes.
     ax.plot(time, videos, label='video')  # Plot more data on the axes...
     ax.plot(time, voices, label='voice')  # ... and some more.