Thu May 11 07:28:00 UTC 2023 inscode

test.ipynb

@@ -14,10 +14,56 @@
     }
    ],
    "source": [
-    "import datetime\n",
+    "import numpy as np\n",
+    "import matplotlib.pyplot as plt\n",
     "\n",
-    "today = datetime.date.today()\n",
-    "print(\"今天的日期是: \", today)\n"
+    "\n",
+    "def sigmoid(z):\n",
+    "    return 1 / (1 + np.exp(-z))\n",
+    "\n",
+    "def costFunction(theta, X, y):\n",
+    "    m = len(y)\n",
+    "    J = 0\n",
+    "    grad = np.zeros(theta.shape)\n",
+    "    \n",
+    "    h = sigmoid(np.dot(X, theta))\n",
+    "    J = (-1/m) * np.sum(y*np.log(h) + (1-y)*np.log(1-h))\n",
+    "    grad = (1/m) * np.dot(X.T, (h-y))\n",
+    "    \n",
+    "    return J, grad\n",
+    "\n",
+    "def gradientDescent(X, y, theta, alpha, num_iters):\n",
+    "    m = len(y)\n",
+    "    J_history = np.zeros(num_iters)\n",
+    "    \n",
+    "    for i in range(num_iters):\n",
+    "        J_history[i], grad = costFunction(theta, X, y)\n",
+    "        theta = theta - alpha*grad\n",
+    "        \n",
+    "    return theta, J_history\n",
+    "\n",
+    "# 生成样本数据\n",
+    "np.random.seed(0)\n",
+    "X = np.random.randn(100, 2)\n",
+    "ones = np.ones((100, 1))\n",
+    "X = np.hstack((ones, X))\n",
+    "y = np.random.randint(0, 2, size=(100,1))\n",
+    "\n",
+    "# 初始化theta\n",
+    "initial_theta = np.zeros((X.shape[1], 1))\n",
+    "\n",
+    "# 梯度下降\n",
+    "alpha = 0.1\n",
+    "num_iters = 1000\n",
+    "theta, J_history = gradientDescent(X, y, initial_theta, alpha, num_iters)\n",
+    "\n",
+    "# 绘制决策边界\n",
+    "x1 = np.arange(-3, 3, 0.1)\n",
+    "x2 = -(theta[0]+theta[1]*x1)/theta[2]\n",
+    "plt.plot(x1, x2, label='Decision Boundary')\n",
+    "plt.scatter(X[:, 1], X[:, 2], c=y.flatten())\n",
+    "plt.legend()\n",
+    "plt.show()\n"
    ]
   },
   {
@@ -114,7 +160,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.5"
+   "version": "3.9.5 (default, Nov 23 2021, 15:27:38) \n[GCC 9.3.0]"
   },
   "orig_nbformat": 4,
   "vscode": {