CODEWITHSUNDEEP
python
Batel Carmona
Batel Carmona

Reputation: 19

TypeError: unsupported operand type(s) for ** or pow(): 'list' and 'int'. plt.plot

When I write the following code, I get the following error. What am I doing wrong??

def f(t):
    return np.sin(t**2)

n = 20  # number of points for Riemann integration
a = 0; b = 2
P = np.linspace(a, b, n)  # Standard partition constant width
dt = (b-a)/n
T = [np.random.rand()*dt + p for p in P[:-1]]  # Randomly chosen point

Doing a few more things and then:

plt.figure(figsize=(10,10))

plt.plot(T, f(T), '.', markersize=10)
plt.bar(P[:-1], f(T), width=dt, alpha=0.2, align='edge')

x = np.linspace(a, b, n*100)  # we take finer spacing to get a "smooth" graph
y = f(x)
plt.plot(x, y)
plt.title('Riemann sum with n = {} points'.format(n))
plt.axis('off')
plt.show()

Finally I get the following error: 

    Traceback (most recent call last):
    File "riman.py", line 35, in <module>
    plt.plot(T, f(T), '.', markersize=10)
    File "riman.py", line 11, in f
    return np.sin(t**2)
TypeError: unsupported operand type(s) for ** or pow(): 'list' and 'int'

Upvotes: 1

Views: 277

Answers (1)

meowgoesthedog
meowgoesthedog

Reputation: 15035

The error message is self-explanatory – the power operator ** is not defined for the built-in list type.

They are however defined for np.arrays:

>>> np.array(range(5))**2
array([ 0,  1,  4,  9, 16])

Fix:

T = np.array([np.random.rand()*dt + p for p in P[:-1]])

Upvotes: 1

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