[Python] How can I replace duplicate elements with its first occurrence index in Numpy? (first...

for exmaple, I have two arrays: 'x' for actual values, 'I' for their index in array.

x = [1, 2, 3, 3, 2, 4]
I = [0, 1, 2, 3, 4, 5]


in 'x', the 4th value is duplicate one of 3rd value and the 5th value is duplicate one of 2nd value

Therefore, I want to generate the

y = [0, 1, 2, 2, 1, 5]


(containing first occurrence indicies of original array values)

How can I do this efficiently using python numpy methods?

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