fig = plt.figure(figsize=(15,10))
ax = fig.add_subplot(111)

ax.scatter(gen1['Date'], gen1['load'], marker='o', label='power 1')
ax.scatter(gen2['Date'], gen2['load'], marker='o', label='power 2')
ax.scatter(gen3['Date'], gen3['load'], marker='o', label='power 3')
plt.legend(prop={'size': 12})
plt.title('Power Series', fontsize=16)
plt.xlabel('Date', fontsize=14)
plt.ylabel('Loads', fontsize=14)
plt.show()

Traceback (most recent call last):

  File "<ipython-input-92-93807fb01a43>", line 14, in <module>
    ax.scatter(gen1['Date'], gen1['load'], marker='o', label='power 1')

return _nx.concatenate(arrays, 1)

TypeError: invalid type promotion`