landlab.utils.count_repeats module#

Count repeated values in an array.

count_repeated_values(values)[source]#

Count how many times in an array values repeat and where they appear.

Return a list of length n that gives the values and indices of repeated values. The first element of the list will be the values and indices of all values that appear once or the first time repeated values appear. The next element, values that repeat twice or more, and so on. Thus, the length of the returned list will be the maximum number that any value is repeated in x.

Parameters:: values (array_like) – Input array to count repeated values.
Returns:: List of tuples of (repeated_values, indices).
Return type:: list of tuple

Examples

For an array that contains no repeated values, this function just returns a copy of x, and the indices to each element.

>>> import numpy as np
>>> from landlab.utils.count_repeats import count_repeated_values
>>> counts = count_repeated_values(np.array([20, 30, 40], dtype=int))
>>> len(counts)
1
>>> counts[0]
(array([20, 30, 40]), array([0, 1, 2]))

If x contains a repeated value, the first element contains all unique values along with their indices. For repeated values, return indices to their first occurance. The second element contains values and indices to values occuring two or more times.

>>> counts = count_repeated_values(np.array([20, 30, 40, 30, 30], dtype=int))
>>> len(counts)
3
>>> counts[0]
(array([20, 30, 40]), array([0, 1, 2]))
>>> counts[1]
(array([30]), array([3]))
>>> counts[2]
(array([30]), array([4]))

The input array remains unchanged.

>>> x = np.array([20, 30, 30, 40], dtype=int)
>>> counts = count_repeated_values(x)
>>> x
array([20, 30, 30, 40])