Negate Values in a Range

mediumnumpy_indexing

Implement mask_negate(x, lo, hi).

Given a 1D array x and scalars lo < hi, return a new array equal to x but with every element strictly between lo and hi negated (multiplied by -1). Leave x unchanged. Use a boolean mask — no for/while loops.

Constraints

no scipy, sklearn
no for/while loops

Your solution

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Hints

Hint 1

Build a boolean mask (x > lo) & (x < hi) and flip the sign of those entries in a copy.