Matplotlib scatter plot with unknown error

Question

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:

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''

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

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()

gsmafra · Accepted Answer · 2016-03-01 20:58:11Z

97

Check the scatter documentation. Third argument is for size of points and should be scalar or array_like. I assume 'r' is for color so do the following:

plt.scatter(x, y, c='r')

answered Mar 1, 2016 at 20:58

gsmafra

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1 Comment

Bogdan Janiszewski Over a year ago

Thank you this makes sense now. I was reading it but omitting the c= portion as it is unnecessary in normal plots. It seems silly to have different syntax between the two styles.

cottontail · Accepted Answer · 2023-04-15 04:19:34Z

0

The third positional argument of plot() is fmt= which takes strings of the format '[marker][line][color]' so that each of lines, colors, and markers can be formatted in one go. If you omit line, it becomes a scatter plot. For example, the following two plot the same graph:

plt.plot(x, y, 'ro');

plt.scatter(x, y, color='r');

answered Apr 15, 2023 at 4:19

cottontail

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