Color scatter plot points based on a value in third column?

Question

I am currently plotting a scatterplot based on two columns of data. However, I would like to color the datapoints based on a class label that I have in a third column.

The labels in my third column are either 1,2 or 3. How would I color the scatter plot points based on the values in this third column?

plt.scatter(waterUsage['duration'],waterUsage['water_amount'])
plt.xlabel('Duration (seconds)')
plt.ylabel('Water (gallons)')

DYZ · Accepted Answer · 2017-03-08T00:35:57.590

23

The scatter function happily takes a list of numbers representing color. You can play with a colormap, too, if you want (but you don't have to):

plt.scatter(waterUsage['duration'], waterUsage['water_amount'],\
            c=waterUsage['third_column'], cmap=plt.cm.autumn)

edited Mar 08 '17 at 00:35

answered Mar 08 '17 at 00:26

DYZ

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With your method, how do I know which color corresponds to which number in my `third_column`? – Gary Mar 08 '17 at 19:37
2

Add a colorbar: `plt.colorbar()`. – DYZ Mar 08 '17 at 19:38
Tried with my data, always get `ValueError: 'color' kwarg must be an color or sequence of color specs.` – Jia Gao Aug 23 '21 at 03:30
@JasonGoal In the past 4 years, the function interface changed. – DYZ Aug 23 '21 at 13:55
@DYZ, Would you please kindly update the solution then? – Jia Gao Aug 30 '21 at 04:41

litepresence · Answer 2 · 2017-03-08T01:10:12.253

add another entry to your dictionary "color"

def addcolor(b):

    a=b
    for x in range(len(a['third_column'])):
        if a['third_column'][x]==1: a['color'][x]='rosybrown'
        elif a['third_column'][x]==2: a['color'][x]='papayawhip'
        elif a['third_column'][x]==3: a['color'][x]='chartreuse'
    return a

waterUsage = addcolor(waterUsage)

plt.scatter(waterUsage['duration'], 
            waterUsage['water_amount'],
            c=waterUsage['color'])

matplotlib accepts grayscale, rgb, hex, and html colors:

http://matplotlib.org/api/colors_api.html

html color list, by group:

https://www.w3schools.com/colors/colors_groups.asp

Color scatter plot points based on a value in third column?

2 Answers2