From 3b5be804e225e8e3bd208b9e7c7c8ab6e70ebe37 Mon Sep 17 00:00:00 2001
From: Ignace <ignace@suy.nl>
Date: Sat, 22 Aug 2026 12:08:46 +0200
Subject: [PATCH] betrter y-axis labels

---
 HOWTO.md            | 7 +++++--
 config.yaml         | 6 +++++-
 read_temperature.py | 4 ++++
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/HOWTO.md b/HOWTO.md
index e2649d7..beb9c44 100644
--- a/HOWTO.md
+++ b/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
-lines are drawn at 15, 20, and 25°C by default and can be changed under
+labels can be changed in `config.yaml` under `graph.axes`. Temperature grid
+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
diff --git a/config.yaml b/config.yaml
index 643317d..f9df1f9 100644
--- a/config.yaml
+++ b/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
diff --git a/read_temperature.py b/read_temperature.py
index 3de1517..152bcea 100644
--- a/read_temperature.py
+++ b/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",