Colormap for errorbars

Question

I am trying to match the color of the errorbars with the color of the data points using the code below but I am getting the following error

raise ValueError("RGBA sequence should have length 3 or 4")

ValueError: RGBA sequence should have length 3 or 4

What I am doing wrong? Any advice would be gratefully received.

Data format:

import pandas as pd
import matplotlib.pyplot as plt
import matplotlib as mpl
import matplotlib.style
import matplotlib.font_manager

data = pd.read_csv('error_data')

size = data['size']
x = data['x']
y = data['y']
error = data['error']

plot_xy = plt.scatter(x, y ,s=20,c=size, alpha=0.5) 
colors = plt.colorbar(plot_xy)
size_colors = mpl.colors.to_rgba(size) 
for x, y, e, color in zip(x, y, error ,colors):
    plt.errorbar(x, y, e, lw=1, capsize=3, color=color, alpha=0.5) 
plt.show()

`for x, y, e, color in zip(..., size_colors):` instead of `for x, y, e, color in zip(..., colors):`? — JohanC, Mar 04 '20 at 18:18
can you check if your `size` is a array like [1,2,3,4,5] and not [[1],[2],[3],[4],[5]] — davidbilla, Mar 04 '20 at 18:31

score 1 · Answer 1 · answered Mar 05 '20 at 12:34

Thank you for the help. I managed to get it working from adapting the code (shown below) from this question Colormap for errorbars in x-y scatter plot using matplotlib

import matplotlib.pyplot as plt
import numpy as np

#data
time = np.arange(100.)
signal = time**2
error = np.ones(len(time))*1000

#create a scatter plot
sc = plt.scatter(time,signal,s=0,c=time)

#create colorbar according to the scatter plot
clb = plt.colorbar(sc)

#convert time to a color tuple using the colormap used for scatter
import matplotlib
import matplotlib.cm as cm
norm = matplotlib.colors.Normalize(vmin=min(signal), vmax=max(signal), clip=True)
mapper = cm.ScalarMappable(norm=norm, cmap='viridis')
time_color = np.array([(mapper.to_rgba(v)) for v in signal])

#loop over each data point to plot
for x, y, e, color in zip(time, signal, error, time_color):
    plt.plot(x, y, 'o', color=color)
    plt.errorbar(x, y, e, lw=1, capsize=3, color=color)

Colormap for errorbars

1 Answers1