3.6 Scatter Chart

1. Scatter Plot

In the Line Chart Plot session, we discussed how to use plt.plot() to draw the line chart. It also can be used to produce a scatter chart. Since it is a scatter plot, we can use plt.scatter() as well.

Figure 1.5.1 Simple Scatter Chart

x = np.linspace(0, 10, 50)
y = np.sin(x)

fig,(ax1,ax2) =plt.subplots(1, 2, figsize = (12,6))

ax1.plot(x, y, 'o', color='firebrick')  # plt.plot()
ax1.set_title('plt.plot way')

ax2.scatter(x, y, marker='o', color='m'); # plt.scatter()
ax2.set_title('plt.scatter way')

2. Markers

We can use Markers to customize a scatter plot, make it more stylish.

Marker Type

For example, we use "star" to draw the same curve.

plt.scatter(x, y, marker='*',color='firebrick');

Figure 1.5.3 Star Scatter Plot

More Marker Types

Figure 1.5.4 More Marker Types

Marker Size

plt.figure(1,figsize = (12,6))
plt.plot( x, y, marker='s', markersize=8,label = 'with line')
plt.plot( x+1, y+1, marker='o', markersize=18,linestyle='none',
          label = 'without line')
plt.legend()

Figure 1.5.5 Marker Size Example

Marker Color

x = [3,6,5,7,9,10]
y =[4,2,14, 6,7,3]

sizes = [3080,7000,5000,1000,3200,440]
colors = ['r','y','orange','g','b','c']
plt.figure(figsize =(8,8))
plt.scatter(x, y, c = colors, s = sizes, alpha = 0.7)
plt.title('Marker Colors')

Figure 1.5.6 Marker Colors

Most Used Colors

Figure 1.5.7 Base Colors

Figure 1.5.8 Tableau Palette Colors

Marker Edge

• The color is controlled by the markerfacecolor and markeredgecolor arguments.

• The edge size is controlled by markeredgewidth

plt.figure(1, figsize =(12,6))

plt.plot( x, y, markerfacecolor='skyblue', marker="D", 
         markeredgecolor="black", markersize=16, markeredgewidth =3,
         label = 'thick edge')
         
plt.plot( x+1, y+1, linestyle='none', marker="*", 
         markerfacecolor='yellow', markeredgecolor="black", 
         markersize=24, label = 'thin edge')
plt.legend()

Figure 1.5.9 Marker Edge