[python] How to use the library Matplotlib for drawing graphs

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In deep learning experiments Graph drawing and data visualization are important. With Matplotlib, a library for drawing graphs You can easily draw graphs and visualize data.

Basic usage of Matplotlib.

Using "y = 2x" as an example, specify the following values for drawing.

import numpy as np
import matplotlib.pyplot as plt

#Specifying the drawing range
# x = np.arange(x-axis minimum,Maximum x-axis,Notched)
x = np.arange(0, 6, 0.1)

#a formula
y = 2 * x

#Variables on the horizontal axis. Variables on the vertical axis.
plt.plot(x, y)

#Draw execution
plt.show()

It is drawn and output as follows.

Try changing the formula

Actually draw a graph of a calculation formula other than "y = 2x". If you change the "# calculation formula" part of the code, the graph will change.

When "y = 2 * (x ** 2)"

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(0, 6, 0.1)

#a formula
y = 2 * (x**2)

plt.plot(x, y)
plt.show()

When "y = sin (x)"

#a formula
y = np.sin(x)

Try changing the drawing range.

In the examples so far, the drawing range is set to np.arange (0, 6, 0.1). The calculation formula is y = np.sin (x), and try changing the drawing range.

Draw a range of x-axis (-12 ~ + 12)

x = np.arange(-12, 12, 0.1)

By the way, When specifying with arange, the y-axis is automatically set by the value, so Simply setting the formula to y = 4 * np.sin (x) will expand the y-axis range as shown below.

When you want to fix the drawing range of the y-axis

In the following implementation, the y-axis varies depending on the value of y.

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(0, 6, 0.1)
y = np.sin(x)
plt.plot(x, y)

plt.show()

If you want to fix the y-axis range, Specify the y-axis drawing range with ylim. There is also an xlim that fixes the x-axis range.

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(0, 6, 0.1)
y = np.sin(x)
plt.plot(x, y)

plt.ylim([-4,4])
plt.show()

Try changing the notch

When drawing the following y = np.sin (x), The drawing range was specified by np.arange (0, 6, 0.1). "Numeric increment" can be specified by the third argument of ʻarange`. In this example, it is drawn in 0.1 increments.

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(0, 6, 0.1)
y = np.sin(x)
plt.plot(x, y)
plt.show()

If this is set in 0.5 increments, it will be as follows. The drawing looks like a square.

x = np.arange(0, 6, 0.5)

When drawing two graphs

Draw sin and cos functions at the same time.

import numpy as np
import matplotlib.pyplot as plt

#Specifying the drawing range
x = np.arange(0, 6, 0.1)

#a formula
y1 = np.sin(x)
y2 = np.cos(x)

#Graph drawing settings
plt.plot(x, y1, label="sin") #Label "sin" is added to the y1 graph.
plt.plot(x, y2, linestyle="--", label="cos") #Label "cos" is added to the y2 graph. Specify the line style with linestyle.
plt.xlabel("x") 
plt.xlabel("y")
plt.title('sin & cos')

#Label drawing
plt.legend()
#Graph drawing execution
plt.show()