Searching

NumPy has several functions that can search through arrays, as follows:

  • The argmax function gives the indices of the maximum values of an array.
    >>> a = np.array([2, 4, 8])
>>> np.argmax(a)
2
  • The nanargmax function does the same but ignores NaN values.
    >>> b = np.array([np.nan, 2, 4])
>>> np.nanargmax(b)
2
  • The argmin and nanargmin functions provide similar functionality but pertaining to minimum values.
  • The argwhere function searches for non-zero values and returns the corresponding indices grouped by element.
    >>> a = np.array([2, 4, 8])
>>> np.argwhere(a <= 4)
array([[0],
       [1]])
  • The searchsorted function tells you the index in an array where a specified value could be inserted to maintain the sort order. It uses binary search, which is a O(log n) algorithm. We will see this function in action shortly.
  • The extract function retrieves values from an array based on a condition.
..................Content has been hidden....................

You can't read the all page of ebook, please click here login for view all page.
Reset