Matplotlib scatterplot; colour as a function of a third variable

Question

I want to make a scatterplot (using matplotlib) where the points are shaded according to a third variable. I\'ve got very close with this:

plt.scatter(w, M,          


        

Answer 1

Sometimes you may need to plot color precisely based on the x-value case. For example, you may have a dataframe with 3 types of variables and some data points. And you want to do following,

• Plot points corresponding to Physical variable 'A' in RED.
• Plot points corresponding to Physical variable 'B' in BLUE.
• Plot points corresponding to Physical variable 'C' in GREEN.

In this case, you may have to write to short function to map the x-values to corresponding color names as a list and then pass on that list to the plt.scatter command.

x=['A','B','B','C','A','B']
y=[15,30,25,18,22,13]

# Function to map the colors as a list from the input list of x variables
def pltcolor(lst):
    cols=[]
    for l in lst:
        if l=='A':
            cols.append('red')
        elif l=='B':
            cols.append('blue')
        else:
            cols.append('green')
    return cols
# Create the colors list using the function above
cols=pltcolor(x)

plt.scatter(x=x,y=y,s=500,c=cols) #Pass on the list created by the function here
plt.grid(True)
plt.show()