Keep unique values in an array based on another array while preserving order

Question

I have two array my_arr and distances. For example:

my_arr= np.array([0, 1, 3, 4, 5, 3, 5])
distances = np.array([18, 47, 20, 10, 26, 22, 13])

I would like to get an array of indices whose shape is np.unique(my_arr).size based on the minimum distance. So in the previous example, I would get:

# indices of my_arr
indices_of_my_arr= np.array([0, 1, 2, 3, 6])

Except for loops or map is there a clever way to do this?

EDIT: Another example:

my_arr = np.array([0, 2, 3, 1, 3, 4, 4, 5])
dist = np.array([10, 12, 15, 18, 5, 14, 45, 8])

I expect:

[0, 1, 3, 4, 5, 7]

Divakar · Accepted Answer · 2017-02-07 11:52:37Z

4

You can use np.lexsort and np.unique -

idx = np.lexsort([distances, my_arr])
out = np.sort(idx[np.unique(my_arr[idx], return_index=1)[1]])

edited Feb 7, 2017 at 11:52

answered Feb 7, 2017 at 10:52

Divakar

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2 Comments

floflo29 Over a year ago

I have added another example because your solution does not yield the expected array.

Divakar Over a year ago

@floflo29 Had to add in sort there. Check out the edit.

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