在 matplotlib 的 for 循环中添加 label 和图例

Question

plt.figure(figsize = (8,5))
plt.title('Gas Prices over time in USD', fontdict={'fontname': 'Calibri', 'fontsize': 20})

for country in gas:
    if country != 'Year':
        plt.plot(gas.Year, gas[country], marker = '.')


plt.xticks(gas.Year[::3].tolist()+[2011])
plt.xlabel('Year')

plt.ylabel('US Dollars Per Gallon')

plt.show()

I tried to add a legend based on the columns on my matplotlib graph , I know I have to add labels in order for the legend to display. This is my code, how do I do so in the for loop. Particularly this part:

for country in gas:
    if country != 'Year':
        plt.plot(gas.Year, gas[country], marker = '.', label = ?)

Answer 1

you can pass the column name as label to plt.plot. Then, you can call plt.legend() to draw the legend. Example with dummy data:

gas = pd.DataFrame({'Year': np.arange(10)+2010, 'Cameroon':np.random.randint(0,10,10), 'Nepal':np.random.randint(0,10,10)})


plt.figure(figsize = (8,5))
plt.title('Gas Prices over time in USD', fontdict={'fontname': 'Calibri', 'fontsize': 20})

for country in gas:
    if country != 'Year':
        plt.plot(gas.Year, gas[country], marker = '.', label=country)


plt.xticks(gas.Year[::3].tolist()+[2011])
plt.xlabel('Year')

plt.ylabel('US Dollars Per Gallon')
plt.legend()
plt.show()