matplotlib和numpy 学习笔记

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1. 在二维坐标系中画一个曲线

import matplotlib.pyplot as plt

#data len=400, store int value

data = []

#set x,y轴坐标的范围

plt.axis([0, max(data), 0, 400])

#set value of the points

plt.plot(data, range(400), 'r-')

#反转Y坐标轴方向

plt.gca().invert_yaxis()

#设置x,y轴名称

plt.ylabel('line')

plt.xlabel('greySum')

plt.show()

2. Log transformation

#!/usr/bin/python

import math

import matplotlib.pyplot as plt

import numpy as np

plt.figure(figsize=(,), facecolor='white')

x = np.arange(0.0, 1.0, 0.001)

y=[ t for t in x]

plt.plot(x,y)

v =

c =  / math.log(v+)

y=[c * math.log(v*t+) for t in x]

plt.plot(x,y)

v =

c =  / math.log(v+)

y=[c * math.log(v*t+) for t in x]

plt.plot(x,y)

plt.ylabel('Output intensity level, s')

plt.xlabel('Input intensity level, r')

plt.legend(['y = x', 'y = c*log(x+1)', 'y = c*log(vx+1)'], loc='lower right')

plt.show()