05 - Week/5 - Drawing with Python.ipynb

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  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Practical: Drawing with Python"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Intro to Matplotlib"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "To use Matplotlib you need to import it as follows. Moreover, to extend your jupyter notebook with some extra\n",
    "functionalities for Matplotlib plots you need to use also the magic command `%matplotlib notebook` (In jupyter notebooks\n",
    "magic commands are those that start with a `%` sign).\n",
    "This magic command will make you able to zoom, pan, save plots, etc."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "%matplotlib notebook\n",
    "import matplotlib.pyplot as plt"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "To generate a simple plot you can use the `plot` method of `pyplot`. This method accepts two parameters,\n",
    "the list of x-values and the list y-values:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plt.plot([1, 2, 3, 4], [0, 0, 1, 1])\n",
    "plt.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Before continuing to the next code cell, make sure to close the previous plot otherwise the next `pyplot` command\n",
    "will be overlaid on top of the previous plot. This is also a feature of the magic command.\n",
    "\n",
    "You can use the same method to draw a polygon by providing the coordinates defining the polygon:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plt.plot([1, 1, 2, 2, 1], [0, 1, 1, 0, 0])\n",
    "plt.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The coordinates provided in the previous code cell defines a square. However, this does not look like a square.\n",
    "Does it? To make it look like a square you need to tell `matplotlib` to equalize its axes:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plt.plot([1, 1, 2, 2, 1], [0, 1, 1, 0, 0])\n",
    "plt.axis('equal')\n",
    "plt.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "If you want to draw a filled shape you just need to use `fill` instead of `plot`:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plt.fill([1, 1, 2, 2, 1], [0, 1, 1, 0, 0])\n",
    "plt.axis('equal')\n",
    "plt.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "To quickly format the style of your plot you can use format strings like `ro`. Where `r` stands for red and `o`\n",
    "for dots."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plt.plot([1, 2, 3, 4], [1, 4, 9, 16], 'ro')\n",
    "plt.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You can overlay plots by executing multiple `pyplot` methods one after the other:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plt.fill([1, 1, 2, 2, 1], [0, 1, 1, 0, 0], 'g')\n",
    "plt.plot(1.5, 0.5, 'ro')\n",
    "plt.axis('equal')\n",
    "plt.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "If you want to show a legend about your plot, you need to first label each component of your plot and then call the\n",
    "`legend` method."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plt.fill([1, 1, 2, 2, 1], [0, 1, 1, 0, 0], label='square')\n",
    "plt.plot(1.5, 0.5, 'ro', label='point')\n",
    "plt.axis('equal')\n",
    "plt.legend()\n",
    "plt.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Helper Class Plotter\n",
    "\n",
    "The class defined in the following code cell is a helper class I have provided you for the 1st Assignment. This will\n",
    "help you plotting points and polygons. As you can see, this implements the same commands you have seen above."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "from collections import OrderedDict\n",
    "\n",
    "class Plotter:\n",
    "\n",
    "    def __init__(self):\n",
    "        plt.figure()\n",
    "\n",
    "    def add_polygon(self, xs, ys):\n",
    "        plt.fill(xs, ys, 'lightgray', label='Polygon')\n",
    "\n",
    "    def add_point(self, x, y, kind=None):\n",
    "        if kind == 'outside':\n",
    "            plt.plot(x, y, 'ro', label='Outside')\n",
    "        elif kind == 'boundary':\n",
    "            plt.plot(x, y, 'bo', label='Boundary')\n",
    "        elif kind == 'inside':\n",
    "            plt.plot(x, y, 'go', label='Inside')\n",
    "        else:\n",
    "            plt.plot(x, y, 'ko', label='Unclassified')\n",
    "\n",
    "    def show(self):\n",
    "        handles, labels = plt.gca().get_legend_handles_labels()\n",
    "        by_label = OrderedDict(zip(labels, handles))\n",
    "        plt.legend(by_label.values(), by_label.keys())\n",
    "        plt.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "To use this class, you first need to create a `Plotter` object. Then, you can draw a polygon by providing its\n",
    "coordinates using the `add_polygon` method. Finally, you need to call the method show."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plotter = Plotter()\n",
    "plotter.add_polygon([1, 1, 2, 2, 1], [0, 1, 1, 0, 0])\n",
    "plotter.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You can add a point by using the `add_point` method:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plotter = Plotter()\n",
    "plotter.add_polygon([1, 1, 2, 2, 1], [0, 1, 1, 0, 0])\n",
    "plotter.add_point(1.5, 0.5)\n",
    "plotter.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The added point is considered as an unclassified point. If you want to change the label of this point, you need pass a\n",
    "third argument to the method `add_point`:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plotter = Plotter()\n",
    "plotter.add_polygon([1, 1, 2, 2, 1], [0, 1, 1, 0, 0])\n",
    "plotter.add_point(1.5, 0.5, 'inside')\n",
    "plotter.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Exercise 26\n",
    "\n",
    "Using the `Plotter` object, draw a trapezoid and 3 points: one inside, one outside and one on the boundary of the\n",
    "trapezoid."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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