Matplotlib plot size/legend issue

Question

I'm trying to place the legend in the space underneath a matplotlib plot. I'm creating each subplot with a unique identifier then using plt.figure() to adjust the size of the plot. When I specify a plot size, the space around the plot disappears (the PNG tightens the layout around the plot). Here's my code:

        fig = plt.subplot(111)
        plt.figure(111,figsize=(3,3))
        plots = []
        legend = []
        #fig.set_xlim([0, 20])
        #fig.set_ylim([0, 1])
        #ticks = list(range(len(k_array)))
        #plt.xticks(ticks, k_array)
        plt.plot(k_array, avgNDCG, 'red')
        legend.append("eco overall F1")
        if data_loader.GSQb:
            legend.append("GSQ F1")
            plt.plot(k_array, avgGSQNDCG, 'orange')
        if data_loader.BSQb:
            legend.append("BSQ F1")
            plt.plot(k_array, avgBSQNDCG, 'purple')
        if data_loader.GWQb:
            legend.append("GWQ F1")
            plt.plot(k_array, avgGWQNDCG, 'black')
        if data_loader.BWQb:
            legend.append("BWQ F1")
            plt.plot(k_array, avgBWQNDCG, 'green')
        if data_loader.GAQb:
            legend.append("GAQ F1")
            plt.plot(k_array, avgGAQNDCG, 'blue')
        fig.legend(legend, loc='center', bbox_to_anchor=(0, 0, .7, -2),fontsize='xx-small')
        plt.savefig("RARE " + metaCat + " best avg NDCG scores")

When I comment out plt.figure(111,figsize=(3,3)) , the white space underneath and around the plot is visible:

But when I uncomment it:

Please help me understand how I can modify the plotsize, legend and layout spacing to make it look more like 1 but with a bigger plot.

Answer 1

1. If you add labels to your plot functions, then you won't have to supply legend() with handles and labels - this is more convenient.

2. I would recommend using a loop structure instead of multiple if statements.

3. Regarding the legend, using ncol parameter is going to help you a lot here. You may find the matplotlib documentation legend tutorial helpful

4. If you're working with multiple subplots with different sizes, then I'd recommend using gridspec , otherwise just use plt.subplots() with ncols and nrows parameters. For example:

   fig, axes = plt.subplots(ncols=2, nrows=5, figsize=(12,12))
   axes = axes.flatten() #this results in a 1d array of 10 axes

I simulated your data and implemented what I think you are looking for below.

import pandas as pd
import matplotlib.pyplot as plt
import numpy as np

#simulate data
df = pd.DataFrame({'x' : [1, 2, 3]})
for i in range(11):     
    df['Line_' + str(i)] = np.random.random_sample(3)

fig, ax = plt.subplots(figsize=(12,2.5))

# Change x and y values for troubleshooting purposes
ax.plot(df.x, df.Line_1, 'red', label='eco overall F1')

# This would be a good place to implement a for loop 
# Change all conditions to true for troubleshooting purposes
if True:
    ax.plot(df.x, df.Line_1, 'orange', label='GSQ F1')
if True:
    ax.plot(df.x, df.Line_2, 'purple', label='BSQ F1')
if True:
    ax.plot(df.x, df.Line_3, 'black', label='GWQ F1')
if True:
    ax.plot(df.x, df.Line_4, 'green', label='BWQ F1')
if True:
    ax.plot(df.x, df.Line_5, 'blue', label='GAQ F1')

legend = ax.legend(ncol=4, bbox_to_anchor=(0.5,-0.5), loc='lower center', edgecolor='w')
hide_spines = [ax.spines[x].set_visible(False) for x in ['top','right']]