Add Matrix columnDivide.

Author: markrogoyski

CHANGELOG.md

@@ -6,6 +6,7 @@
 * Matrix `columnAddScalar`
 * Matrix `columnSubtract`
 * Matrix `columnSubtractScalar`
+* Matrix `columnDivide`
 
 ## v2.12.0 - 2025-10-17
 

README.md

@@ -505,6 +505,7 @@ $R = $A->rowSubtractScalar($mᵢ, $k);  // Subtract k from each item of row mᵢ
 $R = $A->columnInterchange($nᵢ, $nⱼ);
 $R = $A->columnExclude($nᵢ);             // Exclude column $nᵢ
 $R = $A->columnMultiply($nᵢ, $k);        // Multiply column nᵢ by k
+$R = $A->columnDivide($nᵢ, $k);          // Divide column nᵢ by k
 $R = $A->columnAdd($nᵢ, $nⱼ, $k);        // Add k * column nᵢ to column nⱼ
 $R = $A->columnAddScalar($n, $k);        // Add k to each item in column nⱼ
 $R = $A->columnAddVector($nᵢ, $V);       // Add Vector V to column nᵢ

src/LinearAlgebra/NumericMatrix.php

@@ -2593,6 +2593,7 @@ public function rowSubtractScalar(int $mᵢ, float $k): NumericMatrix
     /**************************************************************************
      * COLUMN OPERATIONS - Return a Matrix
      *  - columnMultiply
+     *  - columnDivide
      *  - columnAdd
      *  - columnAddScalar
      *  - columnAddVector
@@ -2629,6 +2630,39 @@ public function columnMultiply(int $nᵢ, float $k): NumericMatrix
         return MatrixFactory::createNumeric($R, $this->ε);
     }
 
+    /**
+     * Divide a column by a divisor k
+     *
+     * Each element of Column nᵢ will be divided by k
+     *
+     * @param int   $nᵢ Column to divide
+     * @param float $k divisor
+     *
+     * @return NumericMatrix
+     *
+     * @throws Exception\MatrixException if column to divide does not exist
+     * @throws Exception\BadParameterException if k is 0
+     * @throws Exception\IncorrectTypeException
+     */
+    public function columnDivide(int $nᵢ, float $k): NumericMatrix
+    {
+        if ($nᵢ >= $this->n) {
+            throw new Exception\MatrixException('Column to divide does not exist');
+        }
+        if ($k == 0) {
+            throw new Exception\BadParameterException('Divisor k must not be 0');
+        }
+
+        $m = $this->m;
+        $R = $this->A;
+
+        for ($i = 0; $i < $m; $i++) {
+            $R[$i][$nᵢ] /= $k;
+        }
+
+        return MatrixFactory::createNumeric($R, $this->ε);
+    }
+
     /**
      * Add k times column nᵢ to column nⱼ
      *

tests/LinearAlgebra/Matrix/Numeric/MatrixColumnOperationsTest.php

@@ -119,6 +119,101 @@ public function testColumnMultiplyExceptionColumnGreaterThanN()
         $A->columnMultiply(4, 5);
     }
 
+    /**
+     * @test         columnDivide
+     * @dataProvider dataProviderForColumnDivide
+     * @param        array $A
+     * @param        int   $nᵢ
+     * @param        float $k
+     * @param        array $expectedMatrix
+     * @throws       \Exception
+     */
+    public function testColumnDivide(array $A, int $nᵢ, float $k, array $expectedMatrix)
+    {
+        // Given
+        $A = MatrixFactory::create($A);
+        $expectedMatrix = MatrixFactory::create($expectedMatrix);
+
+        // When
+        $R = $A->columnDivide($nᵢ, $k);
+
+        // Then
+        $this->assertEqualsWithDelta($expectedMatrix, $R, 0.00001);
+    }
+
+    /**
+     * @return array
+     */
+    public function dataProviderForColumnDivide(): array
+    {
+        return [
+            [
+                [
+                    [2, 3, 4],
+                    [4, 6, 8],
+                    [8, 9, 10],
+                ], 0, 2,
+                [
+                    [1, 3, 4],
+                    [2, 6, 8],
+                    [4, 9, 10],
+                ]
+            ],
+            [
+                [
+                    [2, 3, 4],
+                    [4, 6, 8],
+                    [8, 9, 10],
+                ], 0, 2.1,
+                [
+                    [0.952380952380952, 3, 4],
+                    [1.904761904761905, 6, 8],
+                    [3.80952380952381, 9, 10],
+                ]
+            ],
+        ];
+    }
+
+    /**
+     * @test  columnDivide column greater than n
+     * @throws \Exception
+     */
+    public function testColumnDivideExceptionColumnGreaterThanN()
+    {
+        // Given
+        $A = MatrixFactory::create([
+            [1, 2, 3],
+            [2, 3, 4],
+            [3, 4, 5],
+        ]);
+
+        // Then
+        $this->expectException(Exception\MatrixException::class);
+
+        // When
+        $A->columnDivide(4, 5);
+    }
+
+    /**
+     * @test   columnDivide K is zero
+     * @throws \Exception
+     */
+    public function testColumnDivideExceptionKIsZero()
+    {
+        // Given
+        $A = MatrixFactory::create([
+            [1, 2, 3],
+            [2, 3, 4],
+            [3, 4, 5],
+        ]);
+
+        // Then
+        $this->expectException(Exception\BadParameterException::class);
+
+        // When
+        $A->columnDivide(2, 0);
+    }
+
     /**
      * @test         columnAdd
      * @dataProvider dataProviderForColumnAdd