Need help please. Jupyter Notebook : For one of my classes we are using Juypter to make graphs and all that good stuff. Coding is not my thing, and I usually try to follow my instuctor, but I don't think he's got Juypter down. We are trying to add letters to a chart. Here's the command we were given (I did add the numbers to the cell above):


    plt.scatter(spectralClass, apparentMagnitude)
    plt.title('H-R Diagram Cluster A')
    plt.xlabel('Spectral Class')
    plt.xticks( (0, 1, 2, 3, 4, 5, 6), ('B', 'A', 'F', 'G', 'K', 'M', '') )
    plt.ylabel('Apparent Magnitude') 
    plt.gca().invert_yaxis()
    plt.rcParams['figure.figsize'] = (10,10)
    plt.show()

**I keep getting this error: 

    NameError                                 Traceback (most recent call last)
    <ipython-input-67-385bd2daa1cd> in <module>()
    ----> 1 plt.scatter(spectralClass, apparentMagnitude)
          2 plt.title('H-R Diagram Cluster A')
          3 plt.xlabel('Spectral Class')
          4 plt.xticks( (0, 1, 2, 3, 4, 5, 6), ('B', 'A', 'F', 'G', 'K', 'M', '') )
          5 plt.ylabel('Apparent Magnitude')
    
    NameError: name 'apparentMagnitude' is not defined[enter image description here][1]


  [1]: https://i.stack.imgur.com/5sGXB.png