How to plot color as function of a third variable using matplotlib.scatter?

Question

I want to plot Points with x and y-Values and colour them depending on a corresponding time value. Data is stored in a Dataframe.

The solution should be the c-parameter of matplotlib's scatter function, but for some reason its not working for me. The times-column is a List of float values between 0 and 3. Plotting the Points without c-parameter is working.

import matplotlib.pyplot as plt

c=list(df_result_local['times'])
for i in range(len(df_result_local['Points'])):
    plt.scatter(df_result_local['Points'][i].x, df_result_local['Points'][i].y, c=c, alpha = 0.5)

Here I get a ValueError: 'c' argument has 1698 elements, which is not acceptable for use with 'x' with size 1, 'y' with size 1.

Well your error states, that your x and y axis have a length of 1, while c has a length of 1698. So you probably have to convert x and y to lists as well. — Nils
– Nils, Commented Nov 4, 2019 at 9:40
You need to convert c[i] to a color of your liking. See matplotlib.org/tutorials/colors/colormaps.html Viridis is often considered an optimal map. — JohanC
– JohanC, Commented Nov 4, 2019 at 9:41
x,y are the same? I mean, if x = 0, y = 0 and x = 5, y =5 and so on? You are getting x and y from the same pandas column, it's not wrong, but it's a bit weirdo. — powerPixie
– powerPixie, Commented Nov 4, 2019 at 9:41

Clément · Accepted Answer · 2019-11-04 09:49:57Z

1

Try this

import matplotlib.pyplot as plt

c=list(df_result_local['times'])
x = []
y = []
for i in range(len(df_result_local['Points'])):
    x.append(df_result_local['Points'][i].x)
    y.append(df_result_local['Points'][i].y)

plt.scatter(df_result_local['Points'][i].x, df_result_local['Points'][i].y, c=c, alpha = 0.5)

answered Nov 4, 2019 at 9:49

Clément

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Comments

KPLauritzen · Accepted Answer · 2019-11-04 09:40:15Z

0

I think you need to use the index on c as well. So

plt.scatter(df_result_local['Points'][i].x, df_result_local['Points'][i].y, c=c[i], alpha = 0.5)

answered Nov 4, 2019 at 9:40

KPLauritzen

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3 Comments

stephank95 Over a year ago

I tried this allready: I get error: tuple index out of range. df_result_local['times'][0] --> 0.31, type(df_result_local['times'][0]) --> numpy.float64

Clément Over a year ago

As it is said in other notes, you need to have same size for c and your data

stephank95 Over a year ago

It is the same size but the point was to handle x and y as lists as well. Thnak you!

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