[Python] How to draw a line graph with Matplotlib

Use plot to draw a line graph. Some examples are shown below.

Drawing a simple line graph

Pass the x, y values separately, like plot (x, y). The line style can be specified with the parameter linestyle.

import numpy as np
import matplotlib.pyplot as plt
from scipy.stats import norm

fig = plt.figure()
ax = fig.add_subplot(1,1,1)

x = np.linspace(-6,6,1000)

ax.plot(x,norm.pdf(x, loc=0.0, scale=1.0), color='black',  linestyle='solid')
ax.plot(x,norm.pdf(x, loc=0.0, scale=0.5), color='black',  linestyle='dashed')
ax.plot(x,norm.pdf(x, loc=0.0, scale=0.25), color='black', linestyle='dashdot')

ax.set_title('First line plot')
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.grid(True)
fig.show()

Change line thickness

You can change the line thickness with linewidth.

import numpy as np
import matplotlib.pyplot as plt
from scipy.stats import norm

fig = plt.figure()
ax = fig.add_subplot(1,1,1)

x = np.linspace(-6,6,1000)

ax.plot(x,norm.pdf(x, loc=0.0, scale=1.0), color='black',  linestyle='solid', linewidth = 3.0, label='line1')
ax.plot(x,norm.pdf(x, loc=0.0, scale=0.5), color='black',  linestyle='dashed',linewidth = 1.0, label='line2')
ax.plot(x,norm.pdf(x, loc=0.0, scale=0.25), color='black', linestyle='dashdot', linewidth = 0.5,label='line3')

ax.set_title('Second line plot')
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.legend()
ax.grid(True)
fig.show()

Change line color

Change the line color with color.

import numpy as np
import matplotlib.pyplot as plt
from scipy.stats import norm

fig = plt.figure()
ax = fig.add_subplot(1,1,1)

x = np.linspace(-6,6,1000)

ax.plot(x,norm.pdf(x, loc=0.0, scale=1.0), color='red',  linestyle='solid', linewidth = 1.0)
ax.plot(x,norm.pdf(x, loc=0.0, scale=0.5), color='green',linestyle='solid',linewidth = 1.0)
ax.plot(x,norm.pdf(x, loc=0.0, scale=0.25), color='blue', linestyle='solid', linewidth = 1.0)

ax.set_title('Third line plot')
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.grid(True)
fig.show()

Draw marker

When marker is specified, marker is drawn at the data location of the line graph. When there is a lot of data, the line disappears with the marker like the line below. By specifying markevery, you can specify how many markers are drawn at intervals.

import numpy as np
import matplotlib.pyplot as plt
from scipy.stats import norm

fig = plt.figure()
ax = fig.add_subplot(1,1,1)

x = np.linspace(-6,6,1000)

ax.plot(x,norm.pdf(x, loc=0.0, scale=1.0), color='black',  linestyle='solid', linewidth = 1.0, marker='o')
ax.plot(x,0.5 + norm.pdf(x, loc=0.0, scale=1.0), color='black',  linestyle='solid', linewidth = 1.0, marker='o', markevery = 50)

ax.set_title('4th line plot')
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.grid(True)
fig.show()