Python Projects for Beginners a ten-Week Bootcamp Approach to Python Programming

Line Plot

Let’s start with the most basic chart we can create, the line plot:

1| # creating a line plot using x and y coords
3| x, y = [ 1600, 1700, 1800, 1900, 2000 ] , [ 0.2, 0.5, 1.1, 2.2, 7.7 ]
5| plt.plot(x, y) # creates the line
7| plt.title("World Population Over Time")
8| plt.xlabel("Year")
9| plt.ylabel("Population (billions)")
11| plt.show( )

Go ahead and run the cell. To start, we create our x and y coordinates for plotting.
The plot() method allows us to plot a single line; it just needs the coordinates passed in. Lines 7, 8, and 9 are all for customizing the chart and its appearance. Lastly, we use the show() method to render the chart. You should output a chart like Figure 10-1.

Figure 10-1. Single line plot of population data
When you want to add more lines to the chart, you simply apply as many plot() methods as necessary. Let’s add some more customization to each plot line this time:

1| # creating a line plot with multiple lines
3| x1, y1 = [ 1600, 1700, 1800, 1900, 2000 ] , [ 0.2, 0.5, 1.1, 2.2, 7.7 ]
4| x2, y2 = [ 1600, 1700, 1800, 1900, 2000 ] , [ 1, 1, 2, 3, 4 ]
6| plt.plot(x1, y1, "rx-", label="Actual") # create a red solid line with x dots
7| plt.plot(x2, y2, "bo--", label="Fake") # create a blue dashed line with circle dots
9| plt.title("World Population Over Time")
10| plt.xlabel("Year")
11| plt.ylabel("Population (billions)")
12| plt.legend( ) # shows labels in best corner
14| plt.show( )

Go ahead and run the cell. By adding a second set of coordinates, we’re able to plot a second line using the plot() method on line 7. We also specified how the lines should render using shorthand syntax. For the third argument in the plot method, we can pass a string that represents the color, symbols for dots, and the line style. Finally, we added a label to each line for making it easy to read the multiline chart, and we’re able to show it by calling the legend() method. The output should look like Figure 10-2.
CHapter 10 INtroduCtIoN to data aNalYsIs

Figure 10-2. Multiline plot of population data