Matplotlib Tutorial - Line Chart

1. Matplotlib Linear Line
2. Matplotlib Curved Line
3. Matplotlib Line Type

We start from plotting the basic chart type - line chart. plot could easily plot out lines like Linear line or curved line, and also have different configuration such as colors, width, marker size, etc.

Matplotlib Linear Line

# -*- coding: utf-8 -*-
import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(0, 9, 10)
y = 2 * x
plt.plot(x, y, "b-")
plt.show()

It plots the line of y=2*x, where x is in the range between 0 and 9.

plt.plot(x, y, "b-")

It plots the data of x and y with a line style of b - blue color and - - solid line.

Matplotlib Curved Line

# -*- coding: utf-8 -*-
import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(0, 4 * np.pi, 1000)
y = np.sin(x)

plt.plot(x, y, "r--")

plt.show()

It generates a sinusoidal waveform, and has the line style as color red - r and dashed line - --.

Matplotlib Line Type

You could change the line type like width, color and line-style with different input arguments in plt.plot() function.

matplotlib.pyplot.plot(*args, **kwargs)

Parameters

**kwargs

Line Color

You have some methods to name the color in the color argument.

Single Letter Alias

The basic built-in colors have the alias as below,

HTML Hex String

You could pass an valid html hex string to the color parameter, like

color = "#f44265"

RGB Tuple

You could also specify the color using an R,G,B tuple, where R, G, B value are in the range of [0, 1] instead of normal range of [0, 255].

The color represented with html hex string above has the RGB value of (0.9569, 0.2588, 0.3891).

color = (0.9569, 0.2588, 0.3891)

Line Style

Matplotlib has 4 built-in line styles,

Line Style
-
--
:
:-

# -*- coding: utf-8 -*-
import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(0, 4 * np.pi, 1000)


for index, line_style in enumerate(["-", "--", ":", "-."]):
    y = np.sin(x - index * np.pi / 2)
    plt.plot(x, y, "k", linestyle=line_style, lw=2)

plt.title("Line Style")
plt.grid(True)

plt.show()

Line Width

You could specify the line width with the parameter linewidth as in

linewidth = 2  # unit is points

or simply use its abbreviation,

lw = 2

# -*- coding: utf-8 -*-
import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(0, 20, 21)

for line_width in [0.5, 1, 2, 4, 8]:
    y = line_width * x
    plt.plot(x, y, "k", linewidth=line_width)

plt.title("Line Width")
plt.grid(True)

plt.show()