matplotlib bar plot add legend from categories dataframe column

I try to add the legend which should, according to my example, output:

1. a red square with the word fruit and
2. a green square with the word veggie.

I tried several things (the example below is just 1 of the many trials), but I can't get it work.

Can someone tell me how to solve this problem?

import pandas as pd from matplotlib import pyplot as plt data = [['apple', 'fruit', 10], ['nanaba', 'fruit', 15], ['salat','veggie', 144]] data = pd.DataFrame(data, columns = ['Object', 'Type', 'Value']) colors = {'fruit':'red', 'veggie':'green'} c = data['Type'].apply(lambda x: colors[x]) bars = plt.bar(data['Object'], data['Value'], color=c, label=colors) plt.legend() 

2 Answers

The usual way to create a legend for objects which are not in the axes would be to create proxy artists as shown in the legend guide

Here,

colors = {'fruit':'red', 'veggie':'green'} labels = list(colors.keys()) handles = [plt.Rectangle((0,0),1,1, color=colors[label]) for label in labels] plt.legend(handles, labels) 

So this is a hacky solution and I'm sure there are probably better ways to do this. What you can do is plot individual bar plots that are invisible using width=0 with the original plot colors and specify the labels. You will have to do this in a subplot though.

import pandas as pd from matplotlib import pyplot as plt data = [['apple', 'fruit', 10], ['nanaba', 'fruit', 15], ['salat','veggie', 144]] data = pd.DataFrame(data, columns = ['Object', 'Type', 'Value']) colors = {'fruit':'red', 'veggie':'green'} c = data['Type'].apply(lambda x: colors[x]) ax = plt.subplot(111) #specify a subplot bars = ax.bar(data['Object'], data['Value'], color=c) #Plot data on subplot axis for i, j in colors.items(): #Loop over color dictionary ax.bar(data['Object'], data['Value'],width=0,color=j,label=i) #Plot invisible bar graph but have the legends specified ax.legend() plt.show()