Map function over subset and recombine.
SubsetMap[f, {e1, e2, …}, {i, j, …}]
SubsetMap[f, expr, {pos1, pos2, …}]
SubsetMap[f, {pos1, pos2, …}]
SubsetMap[Reverse, {a, b, c, d, e}, {2, 4}]
→ {a, d, c, b, e}SubsetMap[Accumulate, {x1, x2, x3, x4, x5, x6}, 2 ;; 5]
→ {x1, x2, x2 + x3, x2 + x3 + x4, x2 + x3 + x4 + x5, x6}