From 9d9e43be2b8fbdc443e1a12e91bb6cd617926322 Mon Sep 17 00:00:00 2001
From: DurieuxPol <durieux.pol@gmail.com>
Date: Fri, 20 Feb 2026 11:01:31 +0100
Subject: [PATCH 1/2] handle special case for single value matrix

---
 src/Math-Matrix/PMMatrix.class.st                  |  2 ++
 src/Math-Matrix/PMSingleValueMatrixHelper.class.st | 13 +++++++++++++
 2 files changed, 15 insertions(+)
 create mode 100644 src/Math-Matrix/PMSingleValueMatrixHelper.class.st

diff --git a/src/Math-Matrix/PMMatrix.class.st b/src/Math-Matrix/PMMatrix.class.st
index 5a57326..125e781 100644
--- a/src/Math-Matrix/PMMatrix.class.st
+++ b/src/Math-Matrix/PMMatrix.class.st
@@ -498,6 +498,8 @@ PMMatrix >> eigen [
 	matrix eigen values.
 	matrix eigen vectors."
 
+	self numberOfColumns == 1 & self numberOfRows == 1 ifTrue: [ ^ PMSingleValueMatrixHelper matrix: self ].
+
 	self isSymmetric
 		ifTrue: [ ^ self asSymmetricMatrix eigen ]
 		ifFalse: [ self error: 'Eigenvalues and eigenvectors of non-symmetric matrix are currently not supported' ]
diff --git a/src/Math-Matrix/PMSingleValueMatrixHelper.class.st b/src/Math-Matrix/PMSingleValueMatrixHelper.class.st
new file mode 100644
index 0000000..34dfdb5
--- /dev/null
+++ b/src/Math-Matrix/PMSingleValueMatrixHelper.class.st
@@ -0,0 +1,13 @@
+Class {
+	#name : 'PMSingleValueMatrixHelper',
+	#superclass : 'PMJacobiTransformationHelper',
+	#category : 'Math-Matrix',
+	#package : 'Math-Matrix'
+}
+
+{ #category : 'initialization' }
+PMSingleValueMatrixHelper >> initialize: aSingleValueMatrix [
+
+	eigenvalues := Array with: (aSingleValueMatrix at: 1 at: 1).
+	eigenvectors := PMVector with: (PMVector ones: 1)
+]

From 2e645ab3c3fbfd24f27540d2937063c74abfc8db Mon Sep 17 00:00:00 2001
From: DurieuxPol <durieux.pol@gmail.com>
Date: Fri, 20 Feb 2026 11:10:17 +0100
Subject: [PATCH 2/2] test

---
 src/Math-Matrix-Tests/PMMatrixTest.class.st | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/Math-Matrix-Tests/PMMatrixTest.class.st b/src/Math-Matrix-Tests/PMMatrixTest.class.st
index 57e7c84..8e82e8b 100644
--- a/src/Math-Matrix-Tests/PMMatrixTest.class.st
+++ b/src/Math-Matrix-Tests/PMMatrixTest.class.st
@@ -163,6 +163,22 @@ PMMatrixTest >> testDimension [
 	
 ]
 
+{ #category : 'linear algebra' }
+PMMatrixTest >> testEigenForSingleValueMatrix [
+
+	| matrix expectedEigenvalues eigenvalues expectedEigenvectors eigenvectors |
+	matrix := PMMatrix rows: #( #( 3 ) ).
+
+	expectedEigenvalues := #( 3 ).
+	expectedEigenvectors := PMVector with: (PMVector ones: 1).
+
+	eigenvalues := matrix eigen values.
+	eigenvectors := matrix eigen vectors.
+
+	eigenvalues with: expectedEigenvalues do: [ :actual :expected | self assert: actual closeTo: expected ].
+	eigenvectors with: expectedEigenvectors do: [ :actual :expected | self assert: actual closeTo: expected ]
+]
+
 { #category : 'linear algebra' }
 PMMatrixTest >> testEigenvalues [
 	"Code Example 8.15"