More Visualization CT @ VT Why Functions How can code be made - PowerPoint PPT Presentation

Introduction to Computational Thinking More Visualization

CT @ VT Why Functions  How can code be made available for others to use?  Cut/paste of code (as we did for Blockly  Python) works only for small amounts of code  Need better ways to organize and reuse large amounts of code  Python provides three ways  Function – code that performs a single action Simple action: round a number  Complex action: generate a visualization   Module – a collection of related functions e.g., all of visualization functions   Package – a collection of related modules e.g., all of the modules that do different forms of  visualization Fall 201 2015 Slide 2

CT @ VT Packages and Modules Matplotlib: commonly used in Python to create visualizations  (see http://matplotlib.org/gallery.html). Syntax: matplotlib.pyplot.show()  Shorthand: import matplotlib.pyplot as plt  ... plt.show() matplotlib module package pyplot show functions plot Fall 201 2015 Slide 3

CT @ VT Functions in 3 easy steps  Step 1: functions have names  show() # show the visualization  Step 2: functions may have parameters  plot(data) # plot the list data  Step 3: functions may return a value  val = sqrt(number) # square root Notes  The user documentation tells you what a function does and what you  need to use it You do not need to know how a function is implemented to use it (and  you often don’t care) Reusing functions is a highly valued professional practice  Fall 201 2015 Slide 4

CT @ VT Three simple visualizations Name Function Typical Usage Name Change or variation (sometimes Line plot plot(x) over time) Scatter plot scatter(x,y) Relation between x and y Histogram hist(x) Distribution over categories of x (aka Bar Chart) Simple statistical measures: mean (average) range (min-max) median (middle value) More complex statistical measures: regressions ….. Fall 201 2015 Slide 5

CT @ VT Line plot visualizations Question: What is the variation in earthquake intensity? import earthquakes # get all the reports of earthquakes of the current day quakes = earthquakes.get_report('day', 'all') quake_list = quakes[“earthquakes”] #create an empty list significance_list = [] for quake in quakes_list: # add the significance of the next earthquake to the list significance_list.append(quake["significance"]) plt.plot(significance_list) plt.show() Click to save Fall 201 2015 Slide 6

CT @ VT Scatter plot visualization Question: What is the relationship between the depth and magnitude of earthquakes? import earthquakes import matplotlib.pyplot as plt … depths = [ … ] magnitudes = […] … plt.scatter(depths, magnitudes) plt.show() Fall 201 2015 Slide 7

CT @ VT Histogram visualization Question: What is the distribution of the magnitudes of earthquakes? import earthquakes import matplotlib.pyplot as plt … magnitudes = [ … ] … plt.hist(magnitudes) plt.show() Fall 201 2015 Slide 8

CT @ VT Next Steps  Work as usual to complete the classwork for today  Homework gives you more practice with these ideas Fall 201 2015 Slide 9