How to set the hue range for a numeric variable using a colored bubble plot in seaborn, python?

Question

I'm trying to use seaborn to create a colored bubbleplot of 3-D points (x,y,z), each coordinate being an integer in range [0,255]. I want the axes to represent x and y, and the hue color and size of the scatter bubbles to represent the z-coordinate.

The code:

import seaborn
seaborn.set()
import pandas
import matplotlib.pyplot

x               = [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200]
y               = [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200]
z               = [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200]

df = pandas.DataFrame(list(zip(x, y, z)), columns =['x', 'y', 'z']) 

ax = seaborn.scatterplot(x="x", y="y",
                 hue="z",
                 data=df)

matplotlib.pyplot.xlim(0,255)
matplotlib.pyplot.ylim(0,255)
matplotlib.pyplot.show()

gets me pretty much what I want:

This however makes the hue range be based on the data in z. I instead want to set the range according to the range of the min and max z values (as 0,255), and then let the color of the actual points map onto that range accordingly (so if a point has z-value 50, then that should be mapped onto the color represented by the value 50 in the range [0,255]).

My summarized question:

• How to manually set the hue color range of a numerical variable in a scatterplot using seaborn?

I've looked thoroughly online on many tutorials and forums, but have not found an answer. I'm not sure I've used the right terminology. I hope my message got across.

Vastah

You might try seaborn.scatterplot(...., hue_norm=(0,255), ...). To avoid confusion, it's best leave out the sizes= when there isn't a size= parameter. – Welcher

I tried with hue_norm=(0,255). Doing so shows uniformly blue circles. I will edit the initial code to avoid the size confusion. – Vastah

Why did you leave out hue="z" ??? hue="z" means to use the z-values to determine the color. hue_norm=(0,255) is meant to give z==0 the lightest color and z==255 the darkest color. – Welcher

An excellent question. My best answer is incompetence =D. To my credit I managed to figure it out before your feedback of keeping the [hue=] parameter =). Thanks for the quick feedback. You solved my problem =) – Vastah

Answer 1

Following @JohanC's suggestion of using hue_norm was the solution. I first tried doing so by removing the [hue=] parameter and only using the [hue_norm=] parameter, which didn't produce any colors at all (which makes sense).

Naturally one should use both the [hue=] and the [hue_norm=] parameters.

import seaborn
seaborn.set()
import pandas
import matplotlib.pyplot

x               = [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200]
y               = [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200]
z               = [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 255]

df = pandas.DataFrame(list(zip(x, y, z, my_sizes)), columns =['x', 'y', 'z']) 

ax = seaborn.scatterplot(x="x", y="y",
                 hue="z", 
                 hue_norm=(0,255),        # <------- the solution
                 data=df)

matplotlib.pyplot.xlim(0,255)
matplotlib.pyplot.ylim(0,255)
matplotlib.pyplot.show()

Vastah