Python: Order of arguments in a defined function

Question

When I evaluate the following function

def f(k,varvz,D,z):
    return np.exp(-(k*(np.sqrt(z**2 + D**2)-D)+(0.041-0.0094*k)*z**2)/varvz)


def g(k,varvz,D):
    return integrate.quad(f,-np.inf,np.inf,args=(k,varvz,D))  

a,err= g(1.24,9.61,1.8)    
print a

I get infand the following error message

inf

c:\users\user1\appdata\local\temp\tmp5iuiuo.py:11: RuntimeWarning: overflow encountered in exp
  return np.exp(-(k*(np.sqrt(z**2 + D**2)-D)+(0.041-0.0094*k)*z**2)/varvz)

But if I change the order of arguments in the definition of f

def f(z,k,varvz,D):
    return np.exp(-(k*(np.sqrt(z**2 + D**2)-D)+(0.041-0.0094*k)*z**2)/varvz)


def g(k,varvz,D):
    return integrate.quad(f,-np.inf,np.inf,args=(k,varvz,D))  

a,err= g(1.24,9.61,1.8)    
print a

I get the desired result 14.5716742277

Why is this so?

Thanks

Shouldn't you also change args=(k,varvz,D)?

awesoon
– awesoon

2015-12-08 09:36:24 +00:00
Commented Dec 8, 2015 at 9:36 — awesoon
– awesoon, Commented Dec 8, 2015 at 9:36
I want to integrate wrt z. k,D,varvz are parameters.

HuShu
– HuShu

2015-12-08 09:40:39 +00:00
Commented Dec 8, 2015 at 9:40 — HuShu
– HuShu, Commented Dec 8, 2015 at 9:40

xnx · Accepted Answer · 2015-12-08 09:45:37Z

3

Your function to integrate (f) needs to be passed the axis to integrate along as the first argument. This is only true of your second definition. See the docs:

func : function

A Python function or method to integrate. If func takes many
arguments, it is integrated along the axis corresponding to the first
argument.

answered Dec 8, 2015 at 9:45

xnx

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