对数坐标图python怎么画_python绘制半对数坐标

实验作图的时候出现了一个问题，由于数据范围过大，导致数据变化不明显，出来的折线图如下：

对应代码：

import matplotlib.pyplot as plt

import numpy as np

a_ = np.array(a)

plt.plot(a_[:, 0],-a_[:, 1])

plt.xlabel('number of objective function evaluations')

plt.ylabel('the optimal solution')

plt.show()

所以想到了利用对数坐标，搜了搜官方文档，将y坐标改成了对数坐标。效果如下：

代码如下：

import matplotlib.pyplot as plt

import numpy as np

a_ = np.array(a)

plt.axes(yscale = "log") # 在plot语句前加上该句话即可

plt.plot(a_[:, 0],-a_[:, 1])

plt.xlabel('number of objective function evaluations')

plt.ylabel('the optimal solution')

plt.show()

如上，在plot前加入语句plt.axes(yscale = "log")即可。若要让x坐标也为对数坐标，yscale改为xscale即可。

注意， 这里用的是matplotlib.pyplot里面的axes，而不是matplotlib.axes里的。

这里使用log关键字，仅用来绘制正数，若要绘制有正数有负数，有symlog关键字可用。

官方文档：https://matplotlib.org/api/_as_gen/matplotlib.pyplot.axes.html#matplotlib.pyplot.axes

附：

这里绘图的数据如下

a = [[1,-536512],

[13,-9950.1],

[24,-9394.13],

[49,-8829.27],

[97,-3496],

[110,-2403.09],

[165,-169.257],

[195,-124.513],

[230,-6.31601],

[245,-7.92737],

[259,-4.78377],

[896,-10.7847],

[1496,-7.73153],

[1679,-6.59467],

[1690,-7.73153],

[2063,-6.59467],

[2064,-7.73153],

[11556,-8.46228],

[16033,-9.08796],

[18108,-17.3727],

[18816,-8.46228],

[19374,-5.23453],

[21550,-4.53278],

[27783,-4.43594],

[27795,-4.53278],

[29177,-4.43594],

[30382,-4.53278],

[46829,-4.2019],

[92000,-4.68217],

[99905,-4.2019],

[148385,-5.23453],

[148501,-4.68217],

[155295,-5.23453],

[155338,-4.86867],

[162962,-5.23453],

[174377,-4.86867],

[256816,-8.46228],

[256879,-4.86867],

[340068,-8.46228],

[340070,-5.23453],

[596774,-5.61897],

[950661,-4.05199],

[951430,-5.61897],

[987355,-4.05199],

[1003312,-5.61897],

[1019746,-4.47187],

[1043041,-5.61897],

[1078970,-4.05199],

[1090274,-5.34352],

[1372887,-2.83073],

[2049744,-2.77323],

[2050511,-2.83073],

[2152576,-2.77323],

[3534190,-4.21561],

[3536974,-2.77323],

[3569699,-4.21561],

[3703846,-2.16943],

[3778351,-4.21561],

[4304789,-2.16943],

[4360274,-1.52345],

[4382029,-2.16943],

[4518296,-4.21561],

[4638560,-2.16943],

[4717278,-4.21561],

[4717910,-2.16943],

[4812802,-4.21561],

[4852083,-2.13751],

[4999685,-4.21561],

[5001974,-1.91082],

[5045584,-4.21561],

[5174315,-2.13751],

[5472105,-4.21561],

[5591650,-2.29429],

[5604518,-4.21561],

[5894536,-1.23585],

[5941052,-4.21561],

[5944566,-1.23585],

[5991252,-4.21561],

[5994778,-1.23585],

[6191307,-2.13751],

[6306965,-2.77323],

[6420408,-1.23585],

[6465015,-2.77323],

[6526275,-1.23585],

[6569227,-2.77323],

[6576564,-1.23585],

[7440708,-2.16943],

[7683774,-3.30138],

[7862138,-1.74225],

[8258342,-3.30138],

[8382625,-1.74225],

[8525884,-3.30138],

[8831033,-1.74225],

[8895660,-3.30138],

[8896294,-1.74225],

[10020372,-1.23585]]