Matplotlib scatter plot with unknown error : <p>I am attempting to create a scatter plot. I have a list of numbers from 0 - 17 as well as an array with 18 values. I can plot the data as a line plot but when I try to plot as a scatter I get an error message I do not understand: <code>TypeError: ufunc 'sqrt' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''</code></p>

<p>What does this error message mean and how can I get the data to plot as a scatter?</p>

<pre><code>import numpy as np
import matplotlib.pyplot as plt

y = [7316.0, 7453.25, 7518.25, 7711.5, 7448.0, 7210.25, 7416.75, 6960.75, 
     7397.75, 6397.5, 5522.75, 5139.0, 5034.75, 4264.75, 5106.0, 3489.5, 
     4712.0, 4770.0]
x = np.arange(0,18,1)

plt.rcParams['legend.loc'] = 'best'
plt.figure(1)
plt.xlim(0, 20)
plt.ylim(0, 10000)
plt.scatter(x, y, 'r')
plt.show()
</code></pre>
