Numpy arithmetic operation between two columns
These types of operations can easily be done using both numpy or pandas. However, in this case I would recommend pandas since it is more intuitive. Using the example array we can create a pandas dataframe:

arr = np.array([[78, 3412, 98, 3441], [106, 3412, 127, 3434], [139, 3411, 160, 3434], [170, 3411, 191, 3442]])
df = pd.DataFrame(arr, columns=['a', 'b', 'c', 'd'])


The two new columns can now be added as follows:

df['e'] = df['a'] - df['c']
df['f'] = df['a'].diff(1)




Directly using numpy, one possible way would be to do:

arr = np.c_[ arr, arr[:,0] - arr[:,2], np.append(np.NaN, arr[1:, 0] - arr[:-1, 0]) ]