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Exercise

2D Arithmetic

Remember how you calculated the Body Mass Index for all baseball players? numpy was able to perform all calculations element-wise (i.e. element by element). For 2D numpy arrays this isn't any different! You can combine matrices with single numbers, with vectors, and with other matrices.

Execute the code below in the IPython shell and see if you understand:

import numpy as np
np_mat = np.array([[1, 2],
                   [3, 4],
                   [5, 6]])
np_mat * 2
np_mat + np.array([10, 10])
np_mat + np_mat

np_baseball is coded for you; it's again a 2D numpy array with 3 columns representing height (in inches), weight (in pounds) and age (in years). baseball is available as a regular list of lists and updated is available as 2D numpy array.

Instructions

100 XP
  • You managed to get hold of the changes in height, weight and age of all baseball players. It is available as a 2D numpy array, updated. Add np_baseball and updated and print out the result.
  • You want to convert the units of height and weight to metric (meters and kilograms, respectively). As a first step, create a numpy array with three values: 0.0254, 0.453592 and 1. Name this array conversion.
  • Multiply np_baseball with conversion and print out the result.