I have a very large `SparseArray` called ` A `. What is the most efficient way to update say element `{i,j}` with value ` x ` to the value `f[x]` ? I worry about **memory usage and code speed** if I need to make like large number of updates. I've seen [Leonid's comment here][1] about a similar problem. But there are a lot of info scattered over old SO site and I am looking for function and a syntax something like `f[A_, {i_,j_}, f_]` that will do the job. I think it is a very essential question for recursive by-element updates to `SparseArrays' and would love to see a complete solution here.

 [1]: http://mathematica.stackexchange.com/questions/276/efficient-way-to-combine-sparsearray-objects/287#287