CODEWITHSUNDEEP
pythonnumpysympycalculus
yerman
yerman

Reputation: 287

'Symbol' object has no attribute 'sin'

I have defined a function integrate_boole as follows:

def integrate_boole(f,l,r,N):
N = 4 * int(N // 4)
h=((r-l)/N)
xN = np.linspace(l,r,N+1)
fN = f(xN)
return ((2*h)/45)*(7*fN[0]+32*(np.sum(fN[1:-1:2]))+12*. (np.sum(fN[2:-2:4]))+14*(np.sum(fN[4:-4]))+7*fN[-1])

I'm now trying to integrate between 0 and pi for f(x), where f(x) is defined as:

def f(x):
return x*np.sin(x)/(1+np.cos(x)**2)

When I substitute f(x) into the function:

integrate_boole(f(x),0,np.pi,8)

I get the following error message:

-----------------------------------------------------------------------  ----
AttributeError                            Traceback (most recent call    last)
<ipython-input-23-91f1a95793b5> in <module>()
----> 1 integrate_boole(f(x),0,np.pi,8)

 <ipython-input-20-165d275ae26c> in f(x)
  1 def f(x):
----> 2     return x*np.sin(x)/(1+np.cos(x)**2)
  3 myx = np.linspace(0,np.pi,1000)
  4 plt.plot(myx,f(myx),label=r"$f(x)=\frac{x\sin{x}}{1+\cos^2{x}}$")
  5 plt.ylabel("$f(x)$")

AttributeError: 'Symbol' object has no attribute 'sin'

I imported the following libraries initially at the beginning of the same notebook:

import numpy as np
import matplotlib.pyplot as plt
import sympy as sym
from ipywidgets.widgets import interact
sym.init_printing(use_latex="mathjax")
x, y, z, t = sym.symbols('x y z t')

I've checked other articles about roughly the same subject, however I don't believe my numpy and sympy libraries are clashing as they seem to have done for other people. But they might be, and I don't know why. Any help would be much appreciated.

Upvotes: 3

Views: 3907

Answers (1)

Eric Duminil
Eric Duminil

Reputation: 54293

The first argument of integrate_boole should be a function.

  • f is a function
  • f(x) is the number returned by the function f for input x.

You need to call 

integrate_boole(f,0,np.pi,8)

and not

integrate_boole(f(x),0,np.pi,8)

Here's the complete code, with correct indentation:

import numpy as np
import matplotlib.pyplot as plt
import sympy as sym

x, y, z, t = sym.symbols('x y z t')

def integrate_boole(f,l,r,N):
    N = 4 * int(N // 4)
    h=((r-l)/N)
    xN = np.linspace(l,r,N+1)
    fN = f(xN)
    return ((2*h)/45)*(7*fN[0]+32*(np.sum(fN[1:-1:2]))+12*(np.sum(fN[2:-2:4]))+14*(np.sum(fN[4:-4]))+7*fN[-1])

def f(x):
    return x*np.sin(x)/(1+np.cos(x)**2)

integrate_boole(f,0,np.pi,8)
# 2.470207745145361

Upvotes: 1

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