betrter y-axis labels

HOWTO.md

@@ -404,8 +404,11 @@ samples existed before the RRD was created.
 
 Temperature uses the left axis with a default range of 0–30°C. Humidity and
 battery use the right axis with a default range of 0–100%. These ranges and
-labels can be changed in `config.yaml` under `graph.axes`. Light-grey reference
+labels can be changed in `config.yaml` under `graph.axes`. Temperature grid
-lines are drawn at 15, 20, and 25°C by default and can be changed under
+labels default to five-degree intervals, and both axes display integers. Since
+RRDtool ties the right axis to the left, the corresponding percentage labels
+are rounded to integers. Light-grey reference lines are drawn at 15, 20, and
+25°C by default and can be changed under
 `graph.axes.temperature.reference_lines`.
 
 The collector also generates `/var/www/html/sensors/index.html`. It displays

config.yaml

@@ -78,6 +78,9 @@ graph:
       minimum: 0
       maximum: 30
       label: degrees C
+      grid_interval: 5
+      label_every_grid_lines: 1
+      number_format: "%.0lf"
       reference_lines:
         - value: 15
           color: D3D3D3
@@ -86,9 +89,10 @@ graph:
         - value: 25
           color: D3D3D3
     percentage:
-      minimum: 0
+      minimum: 10
       maximum: 100
       label: percent
+      number_format: "%.0lf"
   periods:
     day:
       start: end-1d

read_temperature.py

@@ -226,8 +226,12 @@ def render_graphs(sensor: Sensor, rrd_path: Path, config: Config) -> None:
             "--end", str(graph["end"]),
             "--title", f"{sensor.name} - {period['label']}",
             "--vertical-label", str(temperature_axis["label"]),
+            "--y-grid",
+            f"{temperature_axis['grid_interval']}:{temperature_axis['label_every_grid_lines']}",
+            "--left-axis-format", str(temperature_axis["number_format"]),
             "--right-axis", f"{right_axis_scale}:{right_axis_shift}",
             "--right-axis-label", str(percentage_axis["label"]),
+            "--right-axis-format", str(percentage_axis["number_format"]),
             "--lower-limit", str(temperature_minimum),
             "--upper-limit", str(temperature_maximum),
             "--rigid",