02 util:NameError: name 'plt' is not defined

[kzfm]

plt.figure(figsize=(18, 6))
for i in range(0,9):
    plt.subplot(251+i)
    plt.scatter(data[:,i],data_st[:,i])

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-24-81d9a498cf81> in <module>()
----> 1 plt.figure(figsize=(18, 6))
      2 for i in range(0,9):
      3     plt.subplot(251+i)
      4     plt.scatter(data[:,i],data_st[:,i])

NameError: name 'plt' is not defined