import numpy as np
import matplotlib.pyplot as plt

data = np.arange(1000)

a = np.empty((1000, 2))
b = np.empty((2, 1000))

plt.figure()

a[:, 0] = data
plt.psd(a[:, 0])

b[0, :] = data
plt.psd(b[0, :])

plt.show()