car porting examples: add example of plotting the response of brake_pressure vs acceleration (#30958)

* another example

* add comment

* fix that

* oop

* fix link
old-commit-hash: 8d9e431f43d5974d7908aae4645d6fa6fb0e7324

tools/car_porting/README.md

@@ -64,3 +64,11 @@ An example of searching through a database of segments for a specific condition,
 ![steer warning example](https://github.com/commaai/openpilot/assets/9648890/d60ad120-4b44-4974-ac79-adc660fb8fe2)
 
 *a plot of the steer_warning vs steering angle, where we can see it is clearly caused by a large steering angle change*
+
+### [tools/car_porting/examples/subaru_long_accel.ipynb](/tools/car_porting/examples/subaru_long_accel.ipynb)
+
+An example of plotting the response of an actuator when it is active.
+
+![brake pressure example](https://github.com/commaai/openpilot/assets/9648890/8f32cf1d-8fc0-4407-b540-70625ebbf082)
+
+*a plot of the brake_pressure vs acceleration, where we can see it is a fairly linear response.*

tools/car_porting/examples/subaru_long_accel.ipynb

@@ -0,0 +1,120 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "segments = [\n",
+    "  \"d9df6f87e8feff94|2023-03-28--17-41-10/1:12\"\n",
+    "]\n",
+    "platform = \"SUBARU OUTBACK 6TH GEN\"\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import copy\n",
+    "import numpy as np\n",
+    "\n",
+    "from opendbc.can.parser import CANParser\n",
+    "\n",
+    "from openpilot.selfdrive.car.subaru.values import DBC\n",
+    "from openpilot.tools.lib.srreader import SegmentRangeReader\n",
+    "\n",
+    "\"\"\"\n",
+    "In this example, we plot the relationship between Cruise_Brake and Acceleration for stock eyesight.\n",
+    "\"\"\"\n",
+    "\n",
+    "for segment in segments:\n",
+    "  lr = SegmentRangeReader(segment)\n",
+    "\n",
+    "  messages = [\n",
+    "    (\"ES_Distance\", 20),\n",
+    "    (\"ES_Brake\", 20),\n",
+    "    (\"ES_Status\", 20),\n",
+    "  ]\n",
+    "\n",
+    "  cp = CANParser(DBC[platform][\"pt\"], messages, 1)\n",
+    "\n",
+    "  es_distance_history = []\n",
+    "  es_status_history = []\n",
+    "  es_brake_history = []\n",
+    "  acceleration_history = []\n",
+    "\n",
+    "  last_acc = 0\n",
+    "\n",
+    "  for msg in lr:\n",
+    "    if msg.which() == \"can\":\n",
+    "      cp.update_strings([msg.as_builder().to_bytes()])\n",
+    "      es_distance_history.append(copy.copy(cp.vl[\"ES_Distance\"]))\n",
+    "      es_brake_history.append(copy.copy(cp.vl[\"ES_Brake\"]))\n",
+    "      es_status_history.append(copy.copy(cp.vl[\"ES_Status\"]))\n",
+    "\n",
+    "      acceleration_history.append(last_acc)\n",
+    "    \n",
+    "    if msg.which() == \"carState\":\n",
+    "      last_acc = msg.carState.aEgo"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def process(history, func):\n",
+    "  return np.array([func(h) for h in history])\n",
+    "\n",
+    "cruise_activated = process(es_status_history, lambda es_status: es_status[\"Cruise_Activated\"])\n",
+    "cruise_throttle = process(es_distance_history, lambda es_distance: es_distance[\"Cruise_Throttle\"])\n",
+    "cruise_rpm = process(es_status_history, lambda es_status: es_status[\"Cruise_RPM\"])\n",
+    "cruise_brake = process(es_brake_history, lambda es_brake: es_brake[\"Brake_Pressure\"])\n",
+    "acceleration = process(acceleration_history, lambda acc: acc)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import matplotlib.pyplot as plt\n",
+    "\n",
+    "valid_brake = (cruise_activated==1) & (cruise_brake>0) # only when cruise is activated and eyesight is braking\n",
+    "\n",
+    "ax = plt.figure().add_subplot()\n",
+    "\n",
+    "ax.set_title(\"Brake_Pressure vs Acceleration\")\n",
+    "ax.set_xlabel(\"Brake_Pessure\")\n",
+    "ax.set_ylabel(\"Acceleration\")\n",
+    "ax.scatter(cruise_brake[valid_brake], -acceleration[valid_brake])"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.11.4"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}