与python交互拟合

Question

我想用多项式函数拟合一组数据点（我通常使用numpy.polyfit来做），但是我想让用户以交互方式选择多项式的次数。这是我要执行的操作的一个示例：

import sys
import numpy as np
import matplotlib.pyplot as plt
from pylab import *
from sklearn.metrics import mean_squared_error
fig, ax = plt.subplots()
x = np.arange(1,10,0.2)
y = np.sin(x)
ax.plot(x,y,'o',color='orange',markeredgewidth=0.3,markeredgecolor='k')
ax.set_xlim(0,10)
ax.set_ylim(-1.1,1.1)
def press(event):
  #fig.clf()
  fig.canvas.draw_idle()
  sys.stdout.flush()
  deg = int(event.key)
  coeffs = np.polyfit(x,y,deg)
  p = np.poly1d(coeffs)
  rms = sqrt(mean_squared_error(y, p(x)))
  fig.text(0.8,1.02, 'rms='+str(round(rms,4)), rotation=0, color='k',transform=ax.transAxes)
  with open('prova.txt', 'w') as filehandle:
    filehandle.write('#Coefficients for a n= '+str(deg)+' polynomial fit\n\n')
    for listitem in coeffs:
      filehandle.write('%s\n' % listitem)
  ln = plt.plot(x,p(x),'-',color='green',linewidth=0.8,zorder=0)
  fig.canvas.draw()
cid = fig.canvas.mpl_connect('key_press_event', press)
plt.show()
fig.canvas.mpl_disconnect(cid)
f = open('prova.txt','r')
cfs = loadtxt('prova.txt', usecols=(0),comments='#')
print(cfs)

这样，可以有效地拟合点，但是第一个图之后的图被过度绘制。如果我为fig.clf（）删除'＃'，则代码会更新拟合度，但会取消点。

Answer 1

在开始时用None创建全局变量

  txt = None
  ln = None

在press()内部，您可以检查是否已经分配了plot，text和remove()。

  global txt
  global ln

  if txt:
    txt.remove()
  txt = fig.text(0.8,1.02, 'rms='+str(round(rms,4)), rotation=0, color='k',transform=ax.transAxes)

  if ln:
    ln[0].remove()
  ln = plt.plot(x,p(x),'-',color='green',linewidth=0.8,zorder=0)

  fig.canvas.draw()

---

完整代码

import sys
import numpy as np
import matplotlib.pyplot as plt
from pylab import *
from sklearn.metrics import mean_squared_error

# --- functions ---

def press(event):
    global txt
    global ln


    #fig.clf()
    fig.canvas.draw_idle()
    sys.stdout.flush()

    deg = int(event.key)

    coeffs = np.polyfit(x,y,deg)
    p = np.poly1d(coeffs)
    rms = sqrt(mean_squared_error(y, p(x)))

    with open('prova.txt', 'w') as filehandle:
        filehandle.write('#Coefficients for a n= '+str(deg)+' polynomial fit\n\n')
        for listitem in coeffs:
            filehandle.write('%s\n' % listitem)

    if txt:
        txt.remove()
    txt = fig.text(0.8,1.02, 'rms='+str(round(rms,4)), rotation=0, color='k',transform=ax.transAxes)

    if ln:
        ln[0].remove()
    ln = plt.plot(x,p(x),'-',color='green',linewidth=0.8,zorder=0)

    fig.canvas.draw()

# --- main ---

txt = None
ln = None

fig, ax = plt.subplots()
x = np.arange(1,10,0.2)
y = np.sin(x)
ax.plot(x,y,'o',color='orange',markeredgewidth=0.3,markeredgecolor='k')

ax.set_xlim(0,10)
ax.set_ylim(-1.1,1.1)
cid = fig.canvas.mpl_connect('key_press_event', press)
plt.show()

fig.canvas.mpl_disconnect(cid)
f = open('prova.txt','r')
cfs = loadtxt('prova.txt', usecols=(0),comments='#')
print(cfs)