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Exercise

Subsetting 2D NumPy Arrays

If your 2D numpy array has a regular structure, i.e. each row and column has a fixed number of values, complicated ways of subsetting become very easy. Have a look at the code below where the elements "a" and "c" are extracted from a list of lists.

# numpy
import numpy as np
np_x = np.array(x)
np_x[:, 0]

The indexes before the comma refer to the rows, while those after the comma refer to the columns. The : is for slicing; in this example, it tells Python to include all rows.

Instructions

100 XP
  • Print out the 50th row of np_baseball.
  • Make a new variable, np_weight_lb, containing the entire second column of np_baseball.
  • Select the height (first column) of the 124th baseball player in np_baseball and print it out.