Add helper method to find elbow in set of data.

cmeutils/piecewise linear regression.ipynb

@@ -0,0 +1,78 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "9bea9844-da81-4bcc-922e-743f62a968aa",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import numpy as np\n",
+    "import matplotlib.pyplot as plt\n",
+    "import piecewise_regression \n",
+    "#pip install piecewise-regression \n",
+    "#https://github.com/chasmani/piecewise-regression.git\n",
+    "\n",
+    "x = np.load(\"your_file.npy\")\n",
+    "y = np.load(\"your_file.npy\")\n",
+    "\n",
+    "plt.plot(x, y, \"o-\")\n",
+    "plt.xlabel('x_label')\n",
+    "plt.ylabel('y_label')\n",
+    "plt.title('Knee method to sovle for Tg')\n",
+    "\n",
+    "pw_fit = piecewise_regression.Fit(x, y, n_breakpoints=1)\n",
+    "pw_fit.plot_breakpoints(color='r')\n",
+    "\n",
+    "\n",
+    "def find_tg(x,y):\n",
+    "    results=pw_fit.get_results()\n",
+    "    Tg=results['estimates']['breakpoint1']['estimate']\n",
+    "    return Tg\n",
+    "\n",
+    "Tg=find_tg(x,y)\n",
+    "print('Glass transition temperature is:',Tg)\n",
+    "\n",
+    "def find_slope1(x,y):\n",
+    "    results=pw_fit.get_results()\n",
+    "    slope1=results['estimates']['alpha1']['estimate']\n",
+    "    return slope1\n",
+    "\n",
+    "slope1=find_slope1(x,y)\n",
+    "print('Slope before breakpoint1 is:',slope1)\n",
+    "\n",
+    "def find_slope2(x,y):\n",
+    "    results=pw_fit.get_results()\n",
+    "    slope2=results['estimates']['beta1']['estimate']\n",
+    "    return slope2\n",
+    "\n",
+    "slope2=find_slope2(x,y)\n",
+    "print('Slope after breakpoint1 is:',slope2)\n",
+    "\n",
+    "# Print a summary of the fit\n",
+    "pw_fit.summary()"
+   ]
+  }
+ ],
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+   "pygments_lexer": "ipython3",
+   "version": "3.12.3"
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+ "nbformat": 4,
+ "nbformat_minor": 5
+}