Difference between revisions of "Python-3.4.3/C2/Plotting-Charts/English"

Learning Objectives

• Create pie charts
• Create bar charts and
• Find more information on matplotlib

System Specifications

• Ubuntu Linux 14.04 operating system
• Python 3.4.3
• IPython 5.1.0

Pre-requisites

• run basic Python commands on the ipython console
• Load data from files and
• Plot data.

If not, see the relevant Python tutorials on this website.

ipython3

Now, type ipython3 and press Enter.

type %pylab and press Enter.

Type %pylab and press Enter.

Pie chart

pie() function

Syntax:

pie(values, labels= labels)

• values – the data to be plotted
• labels – the label for each wedge in the pie chart

pie inside parentheses values comma labels equal to labels

• where values are the data to be plotted
• and labels – the label for each wedge in the pie chart

Exercise 1

• Plot a pie chart representing the profit percentage of company A.

• Use the data from file company-a-data.txt available in the code file link of this tutorial

Open the file company-a-data.txt and show the content

The first column represents years. The second column represents the profit percentages.

year, profit = loadtxt('company-a-data.txt', unpack = True)

Let us clear the terminal.

Type

year comma profit equal to loadtxt inside parentheses inside single quotes add the path of the file company-a-data.txt comma unpack equal to True and press Enter

unpack equal to True --> returns the transposed array of data.

clf()

pie(profit,labels=year)

Type pie(profit comma labels equal to year) and press Enter.

Show pie chart plot

First one being the values, which is profit in our case.

The next one being the set of labels to be used in the pie chart, which is year in our case.

Exercise 2

Try out the following exercise and resume the video.

Plot a pie chart with the same data with the following colors for each wedges.

• white, red, black, magenta,
• yellow, blue, green, cyan,
• yellow, magenta and blue.

Hint: In your ipython interpreter, try typing pie question mark.

clf()

pie(profit,labels=year,colors=('w','r','k','m','y','b','g','c','y','m','b'))

Clear the plot window by typing clf open and close parentheses and press Enter.

Type pie inside parentheses profit comma labels equal to year comma colors equal to inside parentheses the color codes and press Enter.

This will display a pie chart with each wedge having the color as specified in the parameters.

Bar chart

• with rectangular bars
• with lengths proportional to the values that they represent.

bar() function

bar inside parentheses x comma y

• where x – a sequence of data and
• y - a sequence of data, the same length of x

Exercise 3

• Plot a bar chart representing the profit percentage of company A.

• Use the data from file company-a-data.txt.

clf()

bar(year, profit)

Clear the plot window by typing clf open and close parentheses

Type bar open and close parentheses year comma profit and press Enter.

This will display a bar chart representing the profit percentage of company A

Exercise 4

Hint: Bar chart is not filled and which is hatched with 45^o slanting lines.

The data for the chart may be obtained from the file company-a-data.txt.

Hint: In your ipython interpreter, try typing bar question mark

clf()

bar(year,profit,fill=False,hatch='/')

Clear the plot window by typing clf open and close parentheses

Type bar open and close parentheses year comma profit comma fill equal to False comma hatch equal to inside single quotes slanting line and press Enter.

This will display a bar chart which is not filled and which is hatched with 45^o slanting lines

"Getting help on matplotlib"

{SHOW WEBSITE while narrating}

matplotlib.sourceforge.net/users/screenshots.html

and also at matplotlib.sourceforge.net/gallery.html

More plots can be seen at the following links

Summary slide

In this tutorial we learnt to,

• Plot a pie chart using pie() function
• Plot a bar chart using bar() function
• Access the matplotlib online help

Assignment

• bar(x, y, color='w', hatch='/')
• bar(x, y, fill=False, hatch='//')
• bar(x, y, fill=False, hatch='|')
• bar(x, y, color='w', hatch='\')

1.What statement can be issued to generate a bar chart with vertical line hatching?

Solution to assignment

1. bar x comma y comma fill equal to False comma hatch is equal to a vertical line) is the correct option to generate a bar chart with vertical line hatching.

Forum

Fossee Forum

Textbook Companion

Acknowledgment

http://spoken-tutorial.org

For more details, visit this website.

Thank you.