From d173542e2694d25b00583ff809f670319d8a88fd Mon Sep 17 00:00:00 2001
From: Luc Patiny <luc@patiny.com>
Date: Thu, 28 Jul 2022 10:15:39 +0200
Subject: [PATCH] feat: add xMaxAbsoluteValue

---
 src/index.ts                              |  1 +
 src/x/__tests__/xMaxAbsoluteValue.test.ts | 21 +++++++++++++++
 src/x/xMaxAbsoluteValue.ts                | 32 +++++++++++++++++++++++
 3 files changed, 54 insertions(+)
 create mode 100644 src/x/__tests__/xMaxAbsoluteValue.test.ts
 create mode 100644 src/x/xMaxAbsoluteValue.ts

diff --git a/src/index.ts b/src/index.ts
index 7f2cad32..ff7b525e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -26,6 +26,7 @@ export * from './x/xIsMonotone';
 export * from './x/xIsMonotoneIncreasing';
 export * from './x/xMaxIndex';
 export * from './x/xMaxValue';
+export * from './x/xMaxAbsoluteValue';
 export * from './x/xMean';
 export * from './x/xMeanAbsoluteError';
 export * from './x/xMeanSquaredError';
diff --git a/src/x/__tests__/xMaxAbsoluteValue.test.ts b/src/x/__tests__/xMaxAbsoluteValue.test.ts
new file mode 100644
index 00000000..e16653a4
--- /dev/null
+++ b/src/x/__tests__/xMaxAbsoluteValue.test.ts
@@ -0,0 +1,21 @@
+import { xMaxAbsoluteValue } from '../xMaxAbsoluteValue';
+
+test('xMaxAbsoluteValue', () => {
+  let typedArray = new Int16Array(3);
+  typedArray[0] = 1;
+  typedArray[1] = 2;
+  typedArray[2] = -3;
+
+  expect(xMaxAbsoluteValue([0])).toBe(0);
+  expect(xMaxAbsoluteValue([1])).toBe(1);
+  expect(xMaxAbsoluteValue([1, 2])).toBe(2);
+  expect(xMaxAbsoluteValue([1, 2, 1])).toBe(2);
+  expect(xMaxAbsoluteValue([3, 2, 1])).toBe(3);
+  expect(xMaxAbsoluteValue(typedArray)).toBe(3);
+  expect(xMaxAbsoluteValue([1, 2, 3], { fromIndex: 1 })).toBe(3);
+  expect(xMaxAbsoluteValue([3, 2, 1], { fromIndex: 1 })).toBe(2);
+  expect(xMaxAbsoluteValue([1, 2, 3], { toIndex: 1 })).toBe(2);
+  expect(xMaxAbsoluteValue([3, 2, 1], { toIndex: 1 })).toBe(3);
+  expect(xMaxAbsoluteValue([1, 2, 3], { fromIndex: 1, toIndex: 1 })).toBe(2);
+  expect(xMaxAbsoluteValue([3, 2, 1], { fromIndex: 1, toIndex: 1 })).toBe(2);
+});
diff --git a/src/x/xMaxAbsoluteValue.ts b/src/x/xMaxAbsoluteValue.ts
new file mode 100644
index 00000000..8b1c0cea
--- /dev/null
+++ b/src/x/xMaxAbsoluteValue.ts
@@ -0,0 +1,32 @@
+import { NumberArray } from 'cheminfo-types';
+
+import { xCheck } from './xCheck';
+import { xGetFromToIndex, XGetFromToIndexOptions } from './xGetFromToIndex';
+
+/**
+ * Computes the maximal value of an array of values
+ *
+ * @param array - array of numbers
+ * @param options - options
+ */
+export function xMaxAbsoluteValue(
+  array: NumberArray,
+  options: XGetFromToIndexOptions = {},
+): number {
+  xCheck(array);
+  const { fromIndex, toIndex } = xGetFromToIndex(array, options);
+  let maxValue = array[fromIndex];
+
+  for (let i = fromIndex + 1; i <= toIndex; i++) {
+    if (array[i] >= 0) {
+      if (array[i] > maxValue) {
+        maxValue = array[i];
+      }
+    } else {
+      if (-array[i] > maxValue) {
+        maxValue = -array[i];
+      }
+    }
+  }
+  return maxValue;
+}