TypeError：只能将length-1数组转换为Python标量

Question

我是python的新手，我正在尝试使用梯形规则来近似4个函数的积分，然后找出错误，这个和图，错误与使用的条带的数量，N。

import numpy as np
import pylab as plt

#creating functions of the functions
def f1(x):
    '''this is a function to return f1 = e^(-4x)cos(8*pi*x)'''
    return (np.exp(-4*x))*np.cos(8*np.pi*x)
def f2(x):
    '''this is a function to return f2 = (cos(2*pi*x))^2'''
    return (np.cos(2*np.pi*x))**2
def f3(x):
    '''this is a function to return f3 = sin(2*pi*x)'''
    return np.sin(2*np.pi*x)
def f4(x):
    '''this is a function to return f4 = e^(-((x-5)^2)/0.04)'''
    a = x-.5
    b = a*a
    c = -b
    return np.exp(c/.04) 

x = np.arange (0.0,1.0,0.01)

#plt.figure(1)
#plt.plot(x, f1(x), 'g-', x,  f2(x), 'r--', x, f3(x), 'k--', x, f4(x), 'b--')  
#plt.show()

# N is the number of strips
a=0.0
b= 1
def TrapRule(f,a,b, N):
    '''this a function that appoximates the intregrals of a funtion between
    0 and 1, using the Trapezoidal rule and returns the appoximate value.'''
    #for N in range (3,15):
    H=(b-a)/(N)
    x=H
    c=0.0
    for i in range (1, N-1):
        c += 2*f(x)         
        x += H

    print (H/2)*(f(a)+f(b)+ c)
    return (H/2)*(f(a)+f(b)+ c)

z=np.pi
a= 16*z**2
b= 4+a
c= 1/b
d= np.exp(4)
e=1/d
f= 1-e
F1 = c*f

F2= 0.5
F3 = 0
F4 = 0.199918*((np.pi)**0.5)

#print F1
#TrapRule(f1, .0, 1. , 20000)
#print F2
#TrapRule(f2, .0, 1. , 20000)

#print F3
#TrapRule(f3, .0, 1. , 20000)
#print F4
#TrapRule(f4, .0, 1. , 20000)

def error(F, f, N):  #works
    '''this function caluclate the error from using the TrapRule (compared with real answer)'''
    A = F - TrapRule(f, .0, 1. , N)
    B = A/F
    Er = B*100
    #print Er
    return Er


N1 = np.arange (10, 100, 1)

plt.plot(N1, error(F1, f1, N1), 'g')
plt.show()

当我运行程序时得到错误，

Traceback (most recent call last):
  File "C:\Users\mem208\Portable Python 2.7.6.1\ComAss.py", line 97, in <module>
    plt.plot(N1, error(F1, f1, N1), 'g')
  File "C:\Users\mem208\Portable Python 2.7.6.1\ComAss.py", line 88, in error
    A = F - TrapRule(f, .0, 1. , N)
  File "C:\Users\mem208\Portable Python 2.7.6.1\ComAss.py", line 53, in TrapRule
    for i in range (1, N-1):
TypeError: only length-1 arrays can be converted to Python scalars

谢谢：D

Answer 1

您将N1数组传递到名为error的{​​{1}}，然后将其传递给N，但它仍然是一个数组。

因此行：

TrapRule

实际上是

for i in range (1, N-1)

这没有任何意义。

猜测你可能要做的是：

for i in range(1, np.arange (10, 100, 1)-1)