Python - 從記錄值擬合指數衰減曲線

Question

我知道有與此有關的線程，但我很困惑，我想讓我的數據適合我的數據。

我的數據被導入並繪製成這樣。

import matplotlib.pyplot as plt 
%matplotlib inline 
import pylab as plb 
import numpy as np 
import scipy as sp 
import csv 

FreqTime1 = [] 
DecayCount1 = [] 
with open('Half_Life.csv', 'r') as f: 
    reader = csv.reader(f, delimiter=',') 
    for row in reader: 
     FreqTime1.append(row[0]) 
     DecayCount1.append(row[3]) 

FreqTime1 = np.array(FreqTime1) 
DecayCount1 = np.array(DecayCount1) 

fig1 = plt.figure(figsize=(15,6)) 
ax1 = fig1.add_subplot(111) 
ax1.plot(FreqTime1,DecayCount1, ".", label = 'Run 1') 
ax1.set_xlabel('Time (sec)') 
ax1.set_ylabel('Count') 
plt.legend() 

問題是，我遇到困難設置常規指數衰減，在我不知道如何從數據集中計算的參數值。

如果可能的話，那麼我想要用圖表顯示擬合衰減方程的方程。但是，如果能夠生產出適合的產品，這可以很容易地應用。

編輯 ------------------------------------------- ------------------

所以使用Stanely基R提及

def model_func(x, a, k, b): 
    return a * np.exp(-k*x) + b 

x = FreqTime1 
y = DecayCount1 


p0 = (1.,1.e-5,1.) 
opt, pcov = curve_fit(model_func, x, y, p0) 
a, k, b = opt 

我與此錯誤消息

返回的擬合函數時

TypeError: ufunc 'multiply' did not contain a loop with signature matching types dtype('S32') dtype('S32') dtype('S32')

有關如何解決此問題的任何想法？

Answer 1

你必須使用curve_fit從scipy.optimize：http://docs.scipy.org/doc/scipy-0.16.1/reference/generated/scipy.optimize.curve_fit.html

from scipy.optimize import curve_fit 
import numpy as np 
# define type of function to search 
def model_func(x, a, k, b): 
    return a * np.exp(-k*x) + b 

# sample data 
x = np.array([399.75, 989.25, 1578.75, 2168.25, 2757.75, 3347.25, 3936.75, 4526.25, 5115.75, 5705.25]) 
y = np.array([109,62,39,13,10,4,2,0,1,2]) 

# curve fit 
p0 = (1.,1.e-5,1.) # starting search koefs 
opt, pcov = curve_fit(model_func, x, y, p0) 
a, k, b = opt 
# test result 
x2 = np.linspace(250, 6000, 250) 
y2 = model_func(x2, a, k, b) 
fig, ax = plt.subplots() 
ax.plot(x2, y2, color='r', label='Fit. func: $f(x) = %.3f e^{%.3f x} %+.3f$' % (a,k,b)) 
ax.plot(x, y, 'bo', label='data with noise') 
ax.legend(loc='best') 
plt.show() 

Answer 2

「我與此錯誤消息

TypeError: ufunc 'multiply' did not contain a loop with signature matching types dtype('S32') dtype('S32') dtype('S32') 

如何任何想法返回解決這個問題？「

讀取CSV文件以創建FreqTime1和DelayCount1的代碼正在創建字符串數組。你可以通過@StanleyR在評論中提出的建議來解決這個問題。一個更好的想法是將這段代碼：

FreqTime1 = [] 
DecayCount1 = [] 
with open('Half_Life.csv', 'r') as f: 
    reader = csv.reader(f, delimiter=',') 
    for row in reader: 
     FreqTime1.append(row[0]) 
     DecayCount1.append(row[3]) 

FreqTime1 = np.array(FreqTime1) 
DecayCount1 = np.array(DecayCount1) 

有：

FreqTime1, DecayCount1 = np.loadtxt('Half_Life.csv', delimiter=',', usecols=(0, 3), unpack=True)