CODEWITHSUNDEEP
pythonplotsum
dingo_d
dingo_d

Reputation: 11690

TypeError in python while trying to plot a sum

Since I got the advice to make another question here it goes... I want to plot the sum, and I have a code:

from scitools.std import *
from math import factorial, cos, e, sqrt
from scipy import *
import numpy as np


def f1(t):
    return 0.5*(1 + sum( (a**(2*n)*cos(2*sqrt(1 + n)*t))/(e**a**2*factorial(n)) for n in range(0,100)))

a=4
t = linspace(0, 35, 1000)
y1 = f1(t)

plot(t, y1)

xlabel(r'$\tau$')
ylabel(r'P($\tau$)')
legend(r'P($\tau$)')
axis([0.0, 35.0, 0.0, 1.0])
grid(True)
show()

But I get the error

Traceback (most recent call last):
  File "D:\faxstuff\3.godina\kvantna\vježbe\qm2\v8\plot.py", line 12, in <module>
    y1 = f1(t)
  File "D:\faxstuff\3.godina\kvantna\vježbe\qm2\v8\plot.py", line 8, in f1
    return 0.5*(1 + sum( (a**(2*n)*cos(2*sqrt(1 + n)*t))/(e**a**2*factorial(n)) for n in range(0,100)))
  File "C:\Python26\lib\site-packages\numpy\core\fromnumeric.py", line 1415, in sum
    res = _sum_(a)
  File "D:\faxstuff\3.godina\kvantna\vježbe\qm2\v8\plot.py", line 8, in <genexpr>
    return 0.5*(1 + sum( (a**(2*n)*cos(2*sqrt(1 + n)*t))/(e**a**2*factorial(n)) for n in range(0,100)))
TypeError: unsupported operand type(s) for /: 'numpy.ndarray' and 'numpy.float64'

So what seems to be the problem? It has got to do something with array, but I don't know what :\

EDIT: The picture, in Mathematica looks like this: image

Upvotes: 0

Views: 637

Answers (2)

jscs
jscs

Reputation: 64022

I don't understand what that generator expression is doing at the end of the return statement in f1, but this:

a=4
t = linspace(0, 35, 1000)
y1 = numpy.array([f1(t_i) for t_i in t])

should get you somewhere. What it does is create a new numpy.array by looping through t, calling f1 on each value and building a list from the results. This way the t inside f1 is a single number rather than the whole array at once, which means that your arithmetic can be properly applied to it.

Upvotes: 1

Rafe Kettler
Rafe Kettler

Reputation: 76985

You can't divide a numpy.ndarray by a numpy.float64. This is the problematic code:

return 0.5*(1 + sum( (a**(2*n)*cos(2*sqrt(1 + n)*t))/(e**a**2*factorial(n))

Upvotes: 1

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