From 0a9e050adf6327808914456f8f7bccf5ebb1af69 Mon Sep 17 00:00:00 2001
From: Roberto Moura <r.moura@mwam.com>
Date: Sun, 15 Jun 2025 18:21:35 +0100
Subject: [PATCH] Add support for overriding x tick with non arithmetic
 progression values

---
 plotly/matplotlylib/mpltools.py            | 13 +++++++++--
 plotly/matplotlylib/tests/test_renderer.py | 25 ++++++++++++++++++++++
 2 files changed, 36 insertions(+), 2 deletions(-)
 create mode 100644 plotly/matplotlylib/tests/test_renderer.py

diff --git a/plotly/matplotlylib/mpltools.py b/plotly/matplotlylib/mpltools.py
index 641606b3182..003f6d245b8 100644
--- a/plotly/matplotlylib/mpltools.py
+++ b/plotly/matplotlylib/mpltools.py
@@ -452,9 +452,9 @@ def prep_ticks(ax, index, ax_type, props):
             tick0 = tickvalues[0]
             dticks = [
                 round(tickvalues[i] - tickvalues[i - 1], 12)
-                for i in range(1, len(tickvalues) - 1)
+                for i in range(1, len(tickvalues))
             ]
-            if all([dticks[i] == dticks[i - 1] for i in range(1, len(dticks) - 1)]):
+            if all([dticks[i] == dticks[i - 1] for i in range(1, len(dticks))]):
                 dtick = tickvalues[1] - tickvalues[0]
             else:
                 warnings.warn(
@@ -464,6 +464,8 @@ def prep_ticks(ax, index, ax_type, props):
                 raise TypeError
         except (IndexError, TypeError):
             axis_dict["nticks"] = props["axes"][index]["nticks"]
+            if props["axes"][index]["tickvalues"] is not None:
+                axis_dict["tickvals"] = props["axes"][index]["tickvalues"]
         else:
             axis_dict["tick0"] = tick0
             axis_dict["dtick"] = dtick
@@ -512,6 +514,13 @@ def prep_ticks(ax, index, ax_type, props):
 
     if formatter == "LogFormatterMathtext":
         axis_dict["exponentformat"] = "e"
+    elif formatter == "FuncFormatter" and props["axes"][index]["tickformat"] is not None:
+        to_remove = ["dtick" "tickmode"]
+        for key in to_remove:
+            if key in axis_dict:
+                axis_dict.pop(key)
+        axis_dict["ticktext"] = props["axes"][index]["tickformat"]
+        axis_dict["tickvals"] = props["axes"][index]["tickvalues"]
     return axis_dict
 
 
diff --git a/plotly/matplotlylib/tests/test_renderer.py b/plotly/matplotlylib/tests/test_renderer.py
new file mode 100644
index 00000000000..7ea7559f800
--- /dev/null
+++ b/plotly/matplotlylib/tests/test_renderer.py
@@ -0,0 +1,25 @@
+import plotly.tools as tls
+
+from . import plt
+
+def test_non_arithmetic_progression_xtickvals():
+    xticks = [0.01, 0.53, 0.75]
+    plt.figure()
+    plt.plot([0, 1], [0, 1])
+    plt.xticks(xticks)
+
+    plotly_fig = tls.mpl_to_plotly(plt.gcf())
+
+    assert plotly_fig.layout.xaxis.tickvals == tuple(xticks)
+
+def test_non_arithmetic_progression_xticktext():
+    xtickvals = [0.01, 0.53, 0.75]
+    xticktext = ["Baseline", "param = 1", "param = 2"]
+    plt.figure()
+    plt.plot([0, 1], [0, 1])
+    plt.xticks(xtickvals, xticktext)
+
+    plotly_fig = tls.mpl_to_plotly(plt.gcf())
+
+    assert plotly_fig.layout.xaxis.tickvals == tuple(xtickvals)
+    assert plotly_fig.layout.xaxis.ticktext == tuple(xticktext)