{ "cells": [ { "cell_type": "markdown", "id": "42235b78-7365-4921-8034-a7139a839952", "metadata": { "toc-hr-collapsed": true }, "source": [ "**Mini-workshop \"Getting started with Jupyter notebooks and noto\" 2021** \n", "C. Hardebolle, [CC-BY-NC-SA 4.0](https://creativecommons.org/licenses/by-nc-sa/4.0/)\n", "\n", "
\n", " How to use this notebook?
\n", " This notebook is made of text cells and code cells. The code cells have to be executed to see the result of the program.
To execute a cell, simply select it and click on the \"play\" button (►) in the tool bar just above the notebook, or type shift + enter.
It is important to execute the code cells in their order of appearance in the notebook.\n", "
" ] }, { "cell_type": "markdown", "id": "a2774ae7-2192-4acc-9b04-39a894706ab5", "metadata": {}, "source": [ "# Tutorial: creating interactive visualizations with Matplotlib\n", "\n", "This very short tutorial walks you through the steps for creating an interactive visualization with matplotlib. \n", "Please note that there are *multiple ways* to achieve the same result. This tutorial is just one possible example." ] }, { "cell_type": "markdown", "id": "a7ecbc64-f2c7-4066-ab9c-eeabe7675d06", "metadata": {}, "source": [ "## Technical setup" ] }, { "cell_type": "markdown", "id": "2ca6f8ff-3012-47f2-8f91-f0c05c4ec0a7", "metadata": {}, "source": [ "We need to import two libraries: \n", "* matplotlib for plotting\n", "* ipywidgets for interaction elements such as sliders" ] }, { "cell_type": "code", "execution_count": null, "id": "178a7a7c-86dd-4bad-80ee-70c250708b82", "metadata": {}, "outputs": [], "source": [ "import matplotlib.pyplot as plt\n", "import ipywidgets as widgets" ] }, { "cell_type": "markdown", "id": "8322fb56-37f2-45b0-9c40-2ddfa29eb4b6", "metadata": {}, "source": [ "Before starting to construct a figure, we need to tell matplotlib what we want to generate:\n", "* static images: `%matplotlib inline`\n", "* or dynamic interactive visuals: `%matplotlib widget`" ] }, { "cell_type": "code", "execution_count": null, "id": "2f42895d-8a0a-41b9-aca7-118ed0c476cd", "metadata": {}, "outputs": [], "source": [ "# In this tutorial, we will create an interactive figure\n", "%matplotlib widget" ] }, { "cell_type": "markdown", "id": "c7a1a710-02f9-4ce0-b546-6422f2db7549", "metadata": {}, "source": [ "This setting change the type of `backend` that matplotlib will use. \n", "With the static backend, matplotlib will generate a new image each time we make a modification. \n", "With the interactive backend, only one image will be generated and all the actions and drawings will update the image. \n", "\n", "*Watchout: code written with one backend usually does not work with another backend!*" ] }, { "cell_type": "markdown", "id": "568a1cf2-9745-4396-8575-4d245dfa125a", "metadata": {}, "source": [ "## Data to generate the visualization\n", "Let's generate some data to plot. \n", "In this example we will draw a house and its roof, using sets of x and y coordinates to define points connected by a line." ] }, { "cell_type": "code", "execution_count": null, "id": "29922ff8-37d4-4b1e-9cf6-9fa5d25975c1", "metadata": {}, "outputs": [], "source": [ "# We will plot a rectangle to model a house\n", "house_x = [2, 2, 4, 4]\n", "house_y = [0, 2, 2, 0]\n", "\n", "# We will plot a triangle to model the roof\n", "roof_x = [2, 3, 4]\n", "roof_y = [2, 5, 2]" ] }, { "cell_type": "markdown", "id": "fea1da5d-f18d-48f4-8b4f-e24d3d1cb745", "metadata": {}, "source": [ "## Building the visualization" ] }, { "cell_type": "markdown", "id": "b0530b84-7d3d-4e65-9960-e222f434686f", "metadata": {}, "source": [ "Before starting to build the figure, we first tell matplolib to wait until we tell him to show the figure where we want in the notebook. \n", "If we don't do that, it will start to display the figure right after the first instructions we write." ] }, { "cell_type": "code", "execution_count": null, "id": "9d65ead3-efc7-40f5-823a-306980328261", "metadata": {}, "outputs": [], "source": [ "# Turn the output off for the moment\n", "plt.ioff()" ] }, { "cell_type": "markdown", "id": "22c696c5-f1bb-48cc-b68a-286bea11396e", "metadata": {}, "source": [ "Now let's build the plot. It has two main components:\n", "* a figure, which is an overall container\n", "* one or more \"axes\" i.e. plots" ] }, { "cell_type": "code", "execution_count": null, "id": "f99f07ce-f750-493e-bac0-76427ac83ffb", "metadata": {}, "outputs": [], "source": [ "# Creation of the figure\n", "fig = plt.figure(num='Interactive figure', figsize=(6,4))\n", "\n", "# Creation of one subplot/axe - it will take position index number 1 in a grid of 1 row and 1 column, as described by (nrows, ncols, index)\n", "ax = fig.add_subplot(1,1,1)" ] }, { "cell_type": "markdown", "id": "19d36c78-ecb3-4f17-8199-a48437331805", "metadata": {}, "source": [ "Once we have created these components, we can plot our data. \n", "The `plot` method of the `axe` object plots y versus x as lines and/or markers. It returns the resulting `line` object(s)." ] }, { "cell_type": "code", "execution_count": null, "id": "a061a2e0-1775-4752-8884-88bf00639903", "metadata": {}, "outputs": [], "source": [ "# Plot the house\n", "ax.plot(house_x, house_y)\n", "\n", "# Plot the roof, and get the resulting line, on which we will add interactivity later - NOTICE the syntax with the comma \"roof_line, =\"\n", "roof_line, = ax.plot(roof_x, roof_y)" ] }, { "cell_type": "markdown", "id": "69412705-47f2-40b3-9cd0-95422a0b6309", "metadata": {}, "source": [ "Now let's show the resulting figure! \n", "For that we need to turn on again the interactive mode of matplotlib." ] }, { "cell_type": "code", "execution_count": null, "id": "d940f221-813c-4f52-8fa3-766fd0fa9b2f", "metadata": {}, "outputs": [], "source": [ "# Turn the output on\n", "plt.ion()\n", "\n", "# Show the figure\n", "display(fig.canvas)" ] }, { "cell_type": "markdown", "id": "425f9a44-f36b-417b-a9de-35e855bd5487", "metadata": {}, "source": [ "## Adding some interactivity \n", "Now we can add some interactivity to this plot. For that, we proceed in four steps:\n", "1. We create a slider" ] }, { "cell_type": "code", "execution_count": null, "id": "eadae473-19a9-4f18-b453-4aec54012015", "metadata": {}, "outputs": [], "source": [ "# We create a slider with values ranging from 2 to 10 in steps of .5, by default on value 5\n", "roof_widget = widgets.FloatSlider(min=2, max=10, step=0.5, value=5, description='Roof height:')" ] }, { "cell_type": "markdown", "id": "37549dfa-026c-4ee2-9c45-5e55b06f84b8", "metadata": {}, "source": [ "2. We create a function that will be called when the slider is moved and will update the figure" ] }, { "cell_type": "code", "execution_count": null, "id": "93c29bff-d13f-477f-ab8d-9723856472b1", "metadata": {}, "outputs": [], "source": [ "# This function will be called when the slider is moved\n", "def roof_event_handler(change):\n", " # It allows us to retrieve the new value of the slider\n", " newposition = change.new\n", "\n", " # Then we can update the points of the roof line\n", " roof_line.set_ydata([2, newposition, 2])\n", " \n", " # And finally we tell the figure to update the drawing\n", " #fig.canvas.draw()" ] }, { "cell_type": "markdown", "id": "bfc19f67-fd2a-4d99-a138-3e84c25a962b", "metadata": {}, "source": [ "3. We link the slider to the callback function" ] }, { "cell_type": "code", "execution_count": null, "id": "c7155220-f5f2-40f4-aad6-38d055441646", "metadata": {}, "outputs": [], "source": [ "# Finally we link the widget to the callback function \n", "roof_widget.observe(roof_event_handler, names='value')" ] }, { "cell_type": "markdown", "id": "3242d42a-706b-4040-bf08-a2d118829ab4", "metadata": {}, "source": [ "4. And then we display both the figure and the slider" ] }, { "cell_type": "code", "execution_count": null, "id": "9ebd1106-589f-46ad-b7cd-bfce1db0744a", "metadata": {}, "outputs": [], "source": [ "# Display the figure and the widget (no need to turn the interactive mode on again since we did it earlier)\n", "display(fig.canvas, roof_widget)" ] }, { "cell_type": "markdown", "id": "03b9a626-ee0a-4bec-ba57-d2691252d881", "metadata": {}, "source": [ "Note that the slider udpates both the figure here and also the figure above. \n", "This is the work of the interactive backend!" ] }, { "cell_type": "markdown", "id": "e6c31f99-06b2-42a5-988f-a8e81951b6e2", "metadata": {}, "source": [ "---\n", "\n", "# Your turn now!" ] }, { "cell_type": "markdown", "id": "b4c41719-fe79-4c76-ba62-68e5fbb3edc1", "metadata": {}, "source": [ "
\n", " Activity
\n", "\n", "Add a line to the plot that draws a door to the house. \n", "Then create a slider that will let the user choose the width of the door. \n", " \n", "
" ] }, { "cell_type": "markdown", "id": "206b7ae1-02b9-44d0-9af9-4472df30adbe", "metadata": {}, "source": [ "
\n", "\n", "**Solution** - You can see *one possible solution* by clicking on the \"...\" below.\n", " \n", "
" ] }, { "cell_type": "code", "execution_count": null, "id": "15d0e85e-abc0-4ff1-af59-47eb4c19869b", "metadata": { "jupyter": { "source_hidden": true }, "tags": [] }, "outputs": [], "source": [ "# First define the x and y coordinates of the door\n", "door_x = [2.25, 2.25, 2.50, 2.50]\n", "door_y = [0, 1, 1, 0]\n", "\n", "# Draw the door on the plot and get the resulting line (to be able to update it with the slider)\n", "door_line, = ax.plot(door_x, door_y)\n", "\n", "# Create a widget for the width of the door\n", "door_widget = widgets.FloatSlider(min=0.25, max=1.5, step=0.05, value=0.25, description='Door width:')\n", "\n", "# This function will be called when the door slider is moved\n", "def door_event_handler(change):\n", " # It allows us to retrieve the new value of the slider\n", " newwidth = change.new\n", "\n", " # Then we can change the points of the door line - the figure will update automatically thanks to the interactive mode!\n", " door_line.set_xdata([2.25, 2.25, 2.25+newwidth, 2.25+newwidth])\n", " \n", "\n", "# Finally we link the widget to the callback function \n", "door_widget.observe(door_event_handler, names='value')\n", "\n", "# Let's display again the whole figure with the two sliders\n", "display(fig.canvas, roof_widget, door_widget)" ] }, { "cell_type": "markdown", "id": "9690331e-446d-4062-97d0-069276e335bf", "metadata": {}, "source": [ "---\n", "\n", "# Additional resources\n", "\n", "More on figures and axes of Matplotlib: \n", "https://medium.com/@kapil.mathur1987/matplotlib-an-introduction-to-its-object-oriented-interface-a318b1530aed\n", "\n", "Using the widgets to add interactivity: \n", "https://ipywidgets.readthedocs.io/en/latest/examples/Widget%20Events.html\n", "\n", "Details about the backends of matplotlib: \n", "https://matplotlib.org/3.4.3/users/interactive.html" ] } ], "metadata": { "kernelspec": { "display_name": "Python", "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": "3.8.10" } }, "nbformat": 4, "nbformat_minor": 5 }