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

charts

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.

%pylab and press Enter.

Type %pylab and press Enter.

Pie chart

to illustrate numerical proportion

pie() function

Syntax:

pie(values, labels= labels)

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

pie(values, labels= labels)

• values – the data to be plotted
• 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 line represents years. The second column represents the profit percentages.

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

we first need to load the data from the file using loadtxt command.

Type

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

unpack = True --> returns the transposed array of data

clf()

pie(profit,labels=year)

Type pie(profit,labels=year)

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

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?

clf()

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

Clear the plot window by typing clf()

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

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(x, y)

• x – a sequence of data
• 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()

Type bar(year, profit)

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?

Clue is to try typing bar? In ipython interpreter.

clf()

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

Clear the plot window by typing clf()

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

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}

More plots can be seen at

matplotlib.sourceforge.net/users/screenshots.html

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

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

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

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

Solution to assignment

1. bar(x, y, fill=False, hatch='|') 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.